Hi Everyone,

Today with a warm engine, while driving my 1992 245 (LH 2.4) for 15+ minutes, it instantly started rough running/missing at idle, and accelerating slightly above idle. At 1000rpm + it runs great as always.

When the engine is cold, it idles and runs fine. After it warms, it idles very rough when driving. When it's sitting in park, the idle is fairly smooth with only slight intermittent roughness.

The throttle body is clean, TPS is working and properly adjusted, AMM (cleaned) and ECU are 6 months old. Anything 1000rpm+ runs strong and normal, regardless of temperature.

I'm wondering if it might be the ECT? Its wire is still connected but I haven't tested it.

Any ideas are very appreciated. Thanks, Jim

I solved the problem. It was a vacuum leak in a hose. After replacing older hoses and not finding any leaks, I replaced the newer ones as well. All good now, and I never found the actual leak in a hose.

Next time I will do a smoke test first, then work my way to everything else.


Many thanks to Art and Phil for their help and excellent knowledge of the Volvo 240. You guys are amazing!


Jim

Thanks for the kudos Jim. Your redux sounds a bit vague compared to the analysis you were willing to give it earlier. Sometimes things just "fix themselves" I know, and we shake our heads and accept it. (Faith-based healing fixes injectors too, I guess, Phil.)
--
Art Benstein near Baltimore

"Sometimes I think the greatest talent of all is perseverance. But only sometimes." -Mitch Albom

Art and Phil,

I try to be as analytical as I can, but just accept that it's fixed after never finding a flaw in those newer hoses. I'm sure it's like Phil said, a leak when contorted, something I couldn't find. This has taught me to smoke test first if vacuum leak symptom is suspected.

Another good result is the car runs much better than before, smoother on idle, more power and responsive. Even though I've maintained and driven this car every day for 17 years, small degradations over time go unnoticed, until one day it's passed its limit.

I hope I can be of help to the Volvo community, as you all have been to me.
Jim

Jim, I guess what I'm not clear about, is how you determined it was a mysteriously defective hose. Did you see smoke during a smoke test? Did you change the intake manifold gasket as planned?

It sounds like you replaced some hoses that you didn't suspect before and since then the problem hasn't surfaced. Knowing how you determined it was this (without putting the suspects back and double-checking) would be helpful to others. On the other hand, I recognize fixing old cars isn't lab work.

Which hoses, specifically, are in the suspect list?
--
Art Benstein near Baltimore

Be wary of the man who urges an action in which he himself incurs no risk -Joaquin de Setanti

Art,


Some of the hoses I assumed were good since they were fairly new, but I realized that new parts can be defective, so I thought I should change them.

I suspect it might be the IAC to manifold hose. I tested the old one, put 50 psi on it, nothing. I put it on my vacuum pump at 25 inhg, found nothing. Since it fits under the manifold and seems always under stress, maybe it was contorted to leak? That said, it could have been a different hose as I just went through and did a few when I did the IAC hose.

The intake gasket was next my list, but I fixed the problem before I got there. I probably should go ahead and do it now since this one has 360k miles on it. I need to do the exhaust gasket anyway since I hear a little leak there while under heavy acceleration.

All the Volvo and Indy shop guys said it was a bad IAC. I suspect they replace a lot of them regardless of condition?

As for me, a smoke test from the start would have found the problem without the hassle. I'm still learning.

I plan on doing a compression test as well just to gauge engine/valve condition.
I'm planning on a valve job at 500k. Maybe it won't be needed?

Hi,

Glad to hear you got that thing wrestle down to the ground!

I just kept thinking, that the high idle symptoms was a clue, let alone running rough and it had to be getting too much air from someplace.

These self tuning engines are marvelous as long as you realize just how fast they try to adjust for a small mishap!

If you still have the hoses try checking them with a mity-vac on pressure and vacuum.
A crack can be very small until you bend it or twist it.
I have seen “a” hose actually leak between the internal braiding to the inside. No outside cut or abrasions to give cause for it. No clamp cut nothing! It was rare indeed!

Glad I actually did help you some. I sure was hoping it was not injectors. I want to keep my faith that they are really reliable.

Phil

Hi,

When the engine is idling the slower speed allows for time for little discrepancies to be correct but may get over corrected to cause another set of larger symptoms.

Take a misfiring from the ignition or a lean combination of cylinders, the O2 sensor reports its results and the rpm dropped the ECU jumps in. It can do several things almost simultaneously to try to self-tune it back into a specific program perimeters.
The idle can over compensate by air flow valve shutter or a quick timing move. The latter is used under lean or overheating sensing messages.
I like making sure my ignition system is truly up to the task!

After that,
I would look for a vacuum leakage from the cabin vacuum hose. The hand held vacuum pump does a great job to isolate all vacuum components. The components in the cabin may be leaking off excessive vacuum causing intermittent or full time lean conditions.

On the outside,
Check all hoses connected to the flame trap system. One small hose goes from it to pthe intake manifold. They usually get a crack on the under side that you cannot see easily.
There is a hose going to the idle control valve that might have swollen up some to be too loose?
A crack in the hose to the brake booster, that is a RARE thing but I have found two plastic check valves to go bad or the grommet holding it. It might be worth a strong eyeballing?

Things that affect the AMM calibrated air flow out to the engine.
The black accordion hose volutes and clamps for the ends. Check the other two hose connectors for cracks around their flange welds.

All of the above, in themselves, may not be lasting long enough to trip a check engine code.
The OBD on these cars are not all that sophisticated.
A code is a shotgun blast towards the problem mounted on the side of a barn.
Sometimes, if you don't get a code, good or bad, you will swear it's on the barn door that is swinging!

Just using good basic TLC will do more to keep several things from raising their ugly heads!

Keep in mind, that these old dogs have simple items and have grown some gray hairs!
You just need to use a fine tooth comb, in one hand, while using a combination of rough, or soothing words depending on who's standing around you.
(:-). Step by step, to a parts store or inch by inch of rubber hose, you will get there!

Phil

Hi Phil,

Thanks for the good ideas.


I spent a couple hours checking for vacuum leaks by spraying down every hose and connection. Almost all have been replaced fairly recently and all seem fine after spraying them. I disconnected and plugged the vacuum to the inside. Vacuum gauge shows 19-20 lbs, but dips slightly when the engine misses. When I rev to 1000rpm, I have a solid 21lb of vacuum and it's smooth.

It goes instantly from smooth to rough once a certain temperature is reached. I let it cool, start it again, same thing.

I'll check more possible vacuum, ignition, and ect in the morning.

Thanks much, Jim

I checked the ect resistance and voltage, works perfectly through its temperature range. I check the IAC resistance and voltage, it seems to be working. Maybe I should try cleaning it?

I went over everything and there's no vacuum leaks anywhere. Vacuum gauge 19-20, and solid smooth 21lb at 1000rpm.

I have a Bosch white label ECU 0-280-000-951 in the car. I have a backup remanufactured Bosch unit that I tried and got the same results.

I check all ignition components and it checks good, cap, rotor, wires, coil. The Sparkplugs look good, consistent light tan color.

I'm out of ideas.

"I'm out of ideas. "

Jim, hang your DVM on the oxygen sensor observing the output from cold start through warmup. Do you know what to expect?
--
Art Benstein near Baltimore

"Never trust the work of the last guy, even if you're the last guy"

Hey Art,

That's a good idea and would make sense with the O2/warmup cycle. Now that I think about it, this O2 has a lot of miles on it. Will check it.

Thanks much, Jim

Could be the sensor. But keep in mind, even a good one reports what it sees, and what it sees depends on the ratio of fuel to air determined by all the other factors governing mixture. IOW, don't immediately shoot the messenger. If you read this forum you learn lots of folks have ruined their Bosch air mass meters by hosing them down with "mass airflow sensor cleaner."

Two measurements tell you pretty much all you need to know; oxygen sensor voltage behavior and fuel pressure. Most backyard mechanics lack the means to measure the latter.
--
Art Benstein near Baltimore

Today's mighty oak is just yesterday's nut that held its ground.

Art, the O2 was in the .22-.94 range, so it seems ok? I'll check fuel pressure tomorrow and report back. It should be in the 40psi range?

Jim

Hi

I would be suspicious that the sensor is acting lazy.
Getting a reading at the extreme ends, with a DVM and a read out to display it is staying there too long.
You must have a very nice meter with a very high sampling rates or sometimes called a refreshing speed.

I have a LED light “show” checker that has ten diodes to represent tenths of a volt.
It looks like a one sided drag racing Christmas Tree but all red dots.
It bounces or sweeps up and down very rapidly with only the blinking lights.
A good sensor stays lit more to the center of the column when idling.
It only dips to one extreme or the other when the engine responds to a quick blip of the throttle.
Richer upon opening and leaner when closing.

With this type of graphic like display you can watch its habits.
A nice one is fast and does not hang with hesitation long and so should the ECU be able to react accordingly.
If it were me, I would try another new one, as you can always put it back as a test, to see if the symptoms come back or at least see a change a little to the better.

In the third line of my last post I mentioned the sensor as a great possibility.
Glad to see you are considering it.

Phil

Phil,

Thanks for the info on the O2. My DVM is a decent one but has a slower sampling rate so I'm sure it's not giving numbers in realtime or an average, just a general range.

You have good thoughts on the small cumulative problems that can cause these type symptoms. I was originally looking for a specific faulty part, since this just instantly happened, but it seems like it's that single small straw that got piled upon all those other small straws that maybe broke this Volvo's back.

I'll try a new O2 as I checked and my records show this one has over 80K on it. I thought I changed it earlier but it was my other Volvo.

Thanks much, Jim

I installed a new Bosch O2 sensor and have the same rough idle results.

I tried a different know-good ECU and have the same rough results. Though it did idle a bit higher with this ECU, oddly enough.

I found a slit opening in the AMM to throttle body accordion hose. Fixed it and got the same rough results.

Haven't tested the fuel pressure yet. I did remove the vacuum to the fuel regulator and there was no change at any speed in any way. What does this mean?

Thanks Phil and Art, Jim

When I mentioned being able to learn the most about how the car is running from the behavior at the oxygen sensor output and knowing the fuel pressure, I was speaking in general terms, not suggesting this was a test for rough idle after warm-up.

Rough idle is often caused by mixture being incorrect. If you're not seeing evidence of rich running (gas in the oil, poor mileage, smelly, drowned plugs) it is probably lean. Fuel pressure could be a cause, but if the oxygen sensor is seeing normal behavior; i.e. switching about once a second between lean and rich, you probably won't learn anything new by putting a gauge on the fuel rail.

Assuming it might be lean after warming up, yet the O2 is switching more or less, you could have individual cylinder(s) making it rough. A clogged injector, a fouled plug, an aged ignition wire, an intake manifold with a piece missing, or a valve not closing, maybe. Watching the oxygen sensor with a DVM is like watching a drive-in movie through a freight train compared to using a scope. You get the drift, which is often enough, say, if you're following Dr. Zhivago across the snowy steppes, but you'll miss scenes with any action. That's why you might still have a mixture problem even though you see some lean numbers (like 0.22V) and some rich numbers (like 0.95V) flash up on your DVM display. It just might be cylinder specific.

I've never proved a vacuum leak on our computer managed cars using that old squirt technique you hear touted here all the time. It just doesn't work. If the leak is big enough to fool the idle speed control, which corrects every 1/100 second, you'd hear it, or see it, like that worn ridge in your AMM hose.


--
Art Benstein near Baltimore

Wisdom comes with age, but sometimes age comes alone.

Art, interesting thoughts. I think I'll be spending more time looking for a leak. It does act like a vacuum leak, but seems odd the vacuum readings are pretty good. I guess it doesn't take much of a leak to have big effects with this closed system, and a car with this many miles on it.

Your gasket looks rough. How was that car running?

Jim

I failed to make my point, Jim.

"I guess it doesn't take much of a leak to have big effects with this closed system, and a car with this many miles on it."

Just the reverse. The computer's closed loop feedback and adaptive trim keeps the RPM steady as the engine wear and sealing integrity changes. You can't expect to hear the effects of changes until they fall outside of the range correctable by the loop.

A problem with one cylinder can push the net mixture to overcorrect the remaining three; that's why that intake gasket hole can make the car run rich. You don't hear that in RPM. Odd that you can tell the difference between two ECUs by ear.
--
Art Benstein near Baltimore

You can't trust dogs to watch your food.

Art, that was my mistake. I meant that it might not take much of a leak to go past its limit and have big effects. Sorry about that.

The additional ECU I tested, idled the engine in park at 1200 rpm, the other two idled at a rough 700-800. When in drive, all three idled rough around 500-600. I was using the factory volvo dashboard tach for measurements. It's an automatic with the large tach and small clock. Go figure.

I think it makes sense that over compensating for one cylinder could make the others go in directions they don't need.

I'm going to investigate the injectors and spark plugs again, look for nuance and cause.

I really appreciate your help Art and Phil.

Jim

The IAC should keep idle around half of that. This should not be ECU dependent if they're good ones, and when you swap them, they get their memory entirely reset, so I think it might be worthwhile to repeat this test and be careful about keeping conditions alike. Idle speed should be regulated in park. Loading it with the transmission in gear to regulate it is not required.

The most common natural reason for the IAC to allow high idle is the failure of the throttle position switch to make good contact with foot off the pedal. Blowby oil can permeate the snap action switch part of the TPS. The only sure way to know if this is working properly is to monitor the voltage (using a meter or LED test light) at the ECU pin 2 (yel/white) while you repeatedly step on and off of the accelerator pedal. The "click" is a good way to set it up, but not confirmation the switch is working. An intermittent switch closure is good reason to replace or readjust the TPS and make sure the throttle body is clean.

An unnatural reason is someone has tweaked the throttle plate to adjust idle, leaving more to pass the plate than can be shut down by the idle valve.

Maybe you have a tach because a previous owner installed it? It is a fairly common thing to do, adding the small clock.
--
Art Benstein near Baltimore

THE FOUR STAGES OF LIFE:
1) You believe in Santa Claus.
2) You don't believe in Santa Claus.
3) You are Santa Claus.
4) You look like Santa Claus.

Art,

I again tested the three ECU again back to back, and got the exact same results

I'm thinking the problem might be with the IAC? If I disconnect the wire, the engine speeds up and goes into a rhythmic pattern of rpm from 900-1200. There's no roughness, just that steady rhythm about one cycle per two seconds. When I reconnect, back to the same roughness.

I've checked and adjusted the throttle switch and it seems good. Will check again.

I bought the car in 2002 from the original owner who owns the Volvo dealership in town. It was immaculate, low miles, had a Volvo folder full of every maintenance that had ever been done. He was a purist and a bit of a Volvo nut. I bought a car that was basically new. I'm guessing he had the tach and clock ordered from the factory. The seventeen years I've had it I've tried to keep it up, not as well as he did, but I also didn't have a huge staff of Volvo trained mechanics. It's still is 100% rust free as it's never seen snow, but it did have a repaint as the clearcoat was gone by 2007. I hope to be driving it for another seventeen years.

This one has me a bit stumped. Many things I've just never really thought about on the car has me thinking about them now, because it has mostly been great and problem free.

Thanks, Jim

I ran phase 3 diagnostics. The injectors seemed good. Maybe they aren't consistent with each other, I don't know, but seem to be working ok? The idle air control moves very quickly and firmly open and closed. I would guess this is good. When I cleaned it the other day, it had almost no residue in it, just a slightly tinted cleaner came out.

The sparkplugs look really similar in color and coating. The spark was fat and blue on all of them.

The throttle butterfly and switch is properly adjusted per Volvo. The ECU is receiving signal from it.

I continue to look for vacuum leaks, even on the newer hoses.

Thanks, Jim

I'm a little confused by your last post, in which you say "I again tested the three ECU again back to back, and got the exact same results "

My understanding is you saw a difference in behavior between two ECUs, one giving you a high idle around 1200 rpm. Are you saying that's been verified or discounted? Are there now 3 ECUs to choose from?

Several things you've reported are expected behavior, e.g. the hunting idle with the electrical connector removed from the valve.

The only thing you can tell about the injectors by running OBD mode 3 is they all click. You could tell more if you pulled the rail and clicked them into little jars to measure delivery, but that's an advanced test, and not really what the mode 3 was made for.

When you say properly per volvo*, that should mean exactly the same thing to everyone, right? I don't know what that means. If it still idles 1200 in park, you can plug one of the hoses to the IAC (I use a ziplock bag over the end) to ensure no false air is arriving from another source. The car should barely stay running, i.e. idle at around 3-400 with the IAC circuit blocked. Anything faster, and you've got a vacuum leak bypassing the throttle plate. But if its adjusted "per volvo" it would have to be something other than the throttle plate. The throttle plate adjustment isn't my suspect because of how quickly this showed up -- unless of course problems are being added as you go along.

The sudden onset makes me think of that intake manifold gasket. If the car has low miles, it may be the original gasket, dry as a vermouth. Use your own gut instinct. It really isn't difficult to refresh that gasket. I see Phil is thinking the same as I am.

You're really fortunate to have a car as nice as yours sounds. One previous owner, and babied at that. Best thing is you probably have no DIY hacked repairs to debug; everything done was most likely done right.

*edit: I see your latest response to Phil. Excellent, I think.
--
Art Benstein near Baltimore

Always keep your words soft and sweet, just in case you have to eat them.

Art,

My "I again tested the three ECU again back to back, and got the exact same results " was that all three tested exactly as before with one idling up to 1200. When these were installed in another car they all worked perfectly, smooth idle and running. The other car doesn't have a tach so I didn't check the speed.

My Throttle switch procedure came from a Volvo dealership mechanic who walked me through the procedure. I posted my process in my other post.

It does have the original intake gasket. I went through every record and it has never been replaced. After seeing the one you showed me, I will remove and replace.

This car is a good one, has needed only routine maintenance since I've had it. When I bought it, it was as nearly new. I've used it as my daily work driver/all around vehicle for 17 years. It doesn't really look new anymore, but nice enough that I want to keep it going for another 17+ years. It only stopped on me once, one summer evening while driving across the country and having a few detours. The alternator wire jumped off and the lights ran my battery down. A tow truck driver stopped and asked if I needed help, he jumped me and all was good. Asked the guy what I owed him, he said nothing, said he stole cars for a living and felt he needed to give some good karma, said he was glad to help. Cheers to the Milwaukee repo man.

I still need to buy a VDO volt gauge, not a fan of idiot lights that don't work when you need them.

Art you are a Volvo guru!

Jim

I enjoyed your story about the help you got at the side of the road. Repo man steals cars for a living short on karma! I also urge you follow through with your desire for a voltmeter. The idiot light does not report all charging failure causes, but a voltmeter, whether cigar-lighter plug in cheapie or one right below your clock in the dash is useful.

Over the years I've had trouble with 240s on the road many times, and the overwhelming reason is charging system failure. The brush wear can sneak up on you, as it starts slow and picks up speed as the slip rings wear, so if you figure you can get 50K from a set of brushes based on the last set, check them at 30K next time. A voltmeter warning will give you time enough to drive to a safe place on the battery alone. If you get one for the dash, here's how I made installation easy: http://www.brickboard.com/RWD/volvo/1438600/220/240/260/280/installed_voltmeter.html

I did see your response to Phil on the throttle setup, editing my post to say so. I'm clear now about the "exact same" but left with the mystery of the one ECU that idles high on only one car. That's something that would have me swapping ECUs until the pins wore out trying to learn why! What do you suppose is different about that one that idles high? Surely you set it aside and are working with one of the other two now, because the high idle would otherwise point you to a vacuum leak. That's a head-scratcher to me. Three identical ECUs?

Changing the intake manifold gasket: Goes quickly with a long pattern 13 box end and a 3/8" drive ratchet with a deep 13 socket. Bring a 12 for the bracket where the IAC is attached, and have a magnet tool handy when you take the rearmost nut from cylinder 4 by the firewall. Just the 8 nuts and the bracket bolt.

Oh, how much could be done with a smoke machine!


--
Art Benstein near Baltimore

Always read stuff that will make you look good if you die in the middle of it.

Art,

Yes, the brush block almost got me once, but I noticed that something was obviously wrong since I had a new battery. This was the event that inspired me to look for a gauge, when I learned the light circuit wouldn't notify me of this event. I want a factory gauge but have a problem of where to put it since I have the small Volvo oil pressure gauge underneath the small clock. I was thinking of relocating the radio to the lower compartment and doing the three gauge panel in the radio spot, like the earlier 240s. Do you know if that panel will fit my 92?

I don't understand the ECUs either. My main one is a 951, the backup is a remanufactured 951, and the other I borrowed had no original numbers, just a large label that says remanufactured LH2.4, blah blah, with the company that did it. It was from a 1991.

Thanks for the walkthru on the gauge and the manifold. They will help a lot.

Do you think the throttle switch setup I did was ok?

Jim

Hi Jim,

You do have a lot of thoughts in this thread, each deserving of a thread in itself. The "remanufactured" ECUs scare me. Please tell me, does your fuel rail include a Schrader valve and no cold start valve? So many times on these forums I hear of 92's without the modern rail and 951 ECU which I believed to be universal in 92.

I think the 3-gauge pod will fit. Some of the later car's lower cubbies are short and there was an amp stashed there.

Since Phil made some comment about the throttle setup, I'll add to my remark. My approval was based on the recognition of the procedure from my reading of the 89 factory manual developed even before the first of these LH2.4 cars hit the street. Volvo's official guide said (on p.33 of TP31361) to back the plate off of fully closed by one half turn of the slotted adjustment screw.

I've read many forum debates on "base idle" setting for LH2.4 cars using the two-pin Bosch idle air valve. If you look at that valve in your hands, you see the "limp home" design feature. Look at that opening and think about a young driver stalling at an RR crossing. It is important. Among those debating the procedure for setting that throttle opening screw are folks who understand the working idle valve needs to be able to shut air down enough to reach the idle RPM fixed by the computer's feedback -- under all temperature and engine wear variations. That the adaptive trim capability in LH2.4 needs to be able to cover the "bottom end" of the airflow adjustments.

Many in those debates thought the book recommendation of a half turn was too much, and I suppose wear in the shaft bushings, plate alignment, and other mechanical differences between 1988 when the recommendation was made and 2019 or whenever support those criticisms, so I thought your splitting the difference to 1/4T was "excellent." Besides that, you appear to be careful to not introduce new troubles or at least recognize the opportunities.

TL;DR it seemed to me you knew what you were doing. I'm not as fussy in actual practice, rarely even needing to mess with it, just setting it so the plate can't stick. But, that's too vague to communicate to others.

The switch is another subject. Think of it this way. If you set it too finicky or close to being closed, you have the chance the idle speed won't be regulated when the switch itself messes up. Snap action switches do. They get old. Ask anyone who's worked at Microswitch in Freeport, IL. If you have the switch open after a significant and palpable press on the pedal, that probably won't occur. If your motion before the switch opens is too much, you'll notice it when crawling in traffic, but that would be a lot of pedal travel before it would be affected.

It is always better to understand the system, if you can, as opposed to following a rote procedure.





--
Art Benstein near Baltimore

Mistakes are the portals of discovery. -James Joyce

Art,

My main ECU is a 951, I bought a backup 951 that was remanufactured and worked perfectly when bought it, and currently works perfectly testing it in my friend's 91 240. The third one I tried is from his 91. It has no original numbers so I have no idea what it was before it was rebuilt, but it runs great in the 91.

My rail has no cold start valve and no Schrader.

The way I did throttle switch adjustment was how the certified Volvo mechanic instructed me to do it, as it's how they did them. He's now retired and I don't have contact with him anymore. I wrote out the process, and it clearly states 1/4 turn open on the butterfly and .015" on the switch. I also seems if set to close to absolute close, and the throttle body becomes gunked it would eventually hold the butterfly open slightly (even though it might seal itself decently) and cause the switch to never engage. I hope I said that right. I could try a different setting but somehow feel my problem is elsewhere.

Any ideas on these injectors that have never been cleaned?

Jim

In my search for vacuum leaks I replaced both hoses to the IAC. No difference in the way it runs/idles. While the hoses were off, I plugged its vacuum to the manifold and TB and started it. When cold, it idled smoothly at 500rpm, once it started warming, things got rough.

My next change will be the manifold gasket. Since it's original I guess I should expect it to look like the one you had, Art.

Thanks for all the great ideas and guidance.
Jim

"While the hoses were off, I plugged its vacuum to the manifold and TB and started it. When cold, it idled smoothly at 500rpm, once it started warming, things got rough."

When you did this, the IAC remained connected electrically, right? I would have been very interested in seeing the output of the oxygen sensor (switching rate and excursions) during that warm-up period. Rough is a word for idling we expect everyone to recognize the same, but I'm not so sure I do. Regardless of what it means, the oxygen sensor should be seeing it. If it didn't I'd want to repeat the test with a timing light reading the crank. The manifold gasket it just a guess, based on age and the sudden onset of the symptoms.

Actually that gasket picture I posted is the only one I've ever removed that came out in virtually one piece.
--
Art Benstein near Baltimore

Three engineers and three accountants were traveling by train to a conference. At the station, the three accountants each bought tickets and watched as the three engineers bought only one ticket.

"How are three people going to travel on only one ticket?" asked an accountant.

"Watch and you'll see", answered an engineer.

They all boarded the train. The accountants took their respective seats, but the three engineers all crammed into a rest room and closed the door behind them. Shortly after the train departed, the conductor came around collecting tickets. He knocked on the restroom door and said, "Ticket, please".

The door opened just a crack and a single arm emerged with a ticket in hand.

The conductor took it and moved on.

The accountants saw this and agreed it was a quite clever idea. So, after the conference, the accountants decide to copy the engineers on the return trip and save some money (being clever with money, and all that). When they got to the station, they bought a single ticket for the return trip. To their astonishment, the engineers didn't buy a ticket at all.

"How are you going to ride without a ticket"? said one perplexed accountant.

"Watch and you'll see", answered an engineer.

When they boarded the train, the three accountants crammed into a restroom and the three engineers crammed into another one nearby. The train departed. Shortly afterward, one of the engineers left his restroom and walked over to the restroom where the accountants were hiding. He knocked on the door and said, "Ticket, please."

Art,

While the hoses were off, it was connected electrically.

Any thoughts on the injectors and the fact that they've never been cleaned? I seriously doubt this is the problem, but may be adding to it.

Jim,

You've asked me a couple times so far to speculate about your injectors as an aside, and I can only tell you I've not had a problem yet with an injector on a running car. Did have one clog on one that sat for a while, but that was pretty obvious having a dead cylinder, not a rough idle after warmup. I let the questions go, in the normal fashion waiting for someone (like Dan) with experience enough to answer instead. Do you have your new gasket yet?
--
Art Benstein near Baltimore

I was going to give him a nasty look, but he already had one.

No my local indy shop only had a thin paper gasket, so I'm going to wait for a good quality composite.

If this doesn't fix it I'm going to setup to run a smoke test. Then I will know for sure.

Sorry about the repeat on the injectors, just a thought I had. I may had forgotten to mention it but the car now has 360k miles on it, almost all of them mine. This is the first time it has truly puzzled me.

Hi,

I would advise not to follow the Bentley to the letters in every sentence of that procedure.
I wants you to adjust the throttle stop screw upwards a half turn or more as I remember.

You don’t want to do that as it takes away some of the range of closure of the IAC.
You want it to only touch up to the throttle stop lever and take on just a little pressure of that big spring around the pulley.
Do not turn it upwards anymore because it will start to open the throttle plate. It works out for me to be about the width of the screwdriver slot of a turn!

It’s called a “ stop screw.” It there to keep the big strong spring from banging the plate down inside the bore of the throttle body!

Then, reset the TPS switch to just click as you pick up tension on the pulley and linkage.
Or as ART says, “use a volt or ohmmeter to verify its working by back probing there at the connector.
I think there should be a ECU PIN 2 or 3 but don’t hold me to it. I might be out in left field on the correct pin but if you are at a total loss to what it is, a long shot is available! Art knows!

Another thing to check is the vacuum hose to the brake booster. The easiest way to do it is to have the engine running and squeezing it tightly and only firmly shut. You don’t want to cause harm to the integrity of the hose. Use something with a smooth large radius.
I would say put a couple fingers under there with the pliers but that might hurt! (o -:).
A piece of leather belt spreads the pressure and it won’t hurt your hide in the process.

There should be no change in idle speed when releasing.
If it slows down or idles more smoothly first, you have a bad check valve or booster.
Disclaimer : Unless the hose is leaking really close to the manifold clamp from a gaping split! These hoses are really aged into toughness but there is a lot of vacuum to resist collapsing.

The intake manifold is good too. It’s not very hard as you just lean the whole thing back with the black hose off.

There is plenty of room. I got to be careful when I say that, as with home visitors, there might be another opinion about it! (:-)

Phil

Phil,

This is how I set the throttle butterfly and switch. The throttle body is spotless clean. I closed butterfly completely with the stop screw just resting on the arm. No light can be seen around contact edge, then 1/4 turn open. I set the switch to open with throttle open .015" distance to stop screw. That is how I was taught to set it. Do you think it's ok?

I checked the switch operation continuity and voltage with dvm at the ECU. It checked out good.

I'm still going over vacuum hoses, and will check the brake booster again per your good ideas.

I feel like this is a vacuum leak I haven't found yet.

Another thought I had is about the injectors. They're original and no record they've ever been cleaned. I use occasional Techron and buy quality fuel. The original owner used only quality fuel as he had fleet contracts with a couple companies. Thoughts on injectors?

I really appreciate Phil and Art, Volvo 240 gurus!

Jim

Hi,

Too me, there is no doubt you are getting too much air or the engine couldn’t be turning over that much over idle with the throttle completely closed up in the bore.

I don’t agree with any .015 gap setting, to hold the shaft in a twist. That would opening the throttle plate. You don’t want any what so ever! The “what so ever,” or lack of fit, is enough for some air to always get bye.
I was thinking that if you take the length of the stop lever sticking out on the shaft and compare it one half of the throttle plate diameter, that would be a radius movement equal to the levers length and more possibly!
Since the plate is larger at the bore, it’s got to be holding the outer edge of the plate, opened farther.
Have you done this adjustment with the hose off and seen it after the lever gets stopped?
Also check for slack in the throttle cable draped over the drum pulley. You should be able to pinch it upwards rather easily!

Besides getting it totally closed it works better for the FPR vacuum port hole behind the plate, IMO.
That .015 must be coming in from the old “K” Jet manuals or writers of carburetors in the days that used an anti-run-on solenoids. Those that popped the throttle plates “open more” but still held curb idle when off.

The injectors do have real thick neoprene “O” rings sealing the bodies going into the intake manifold.
A little from each, might accumulate into enough roughness, along with that intake manifold gasket.

As far as Techron, it is pretty much worthless, IMO. Try looking up “Stoddard” solvents. That’s what the label says is in there! Very ambiguous at best to fool the public. High priced paint thinner!

That little bottle added to a big tank of gasoline is so diluted you will never feel a thing!
Octane increases will make for more smoothness and faster starts, for me!
It is very fancy packaging and saying the “Chevron” trademark works on the brain. It makes you think because they make gasoline and charge almost as much as Shell Gasoline that it’s a greater cleaner!

Like you said, you feel that the PO used good gas! With bazillions of gallons going out to the public, the companies need to know enough to cover every fuel system out there! If not, the complaints from all the manufacturers, that build around what is available, would step all over their toes and own their shoes!
The petroleum institute governance of lubricating oils and all the detergents within both directions, would be up reaching up for the low hanging fruit!
The USA probably has the highest standards set from way back! They are always testing and upgrading.

I pretty much say no to snake oils, so why shouldn’t the gasoline be acceptable since we buy so much more of it! Just good fresh clean gasoline free of water condensation from the ground tanks is the best you can do!
Good filters on the car, to stop metal flakes from our gas nozzles banging in the filter necks, is the last line of defense!

Last I knew, water and metal flakes a Stoddard solvent won’t remove.

People buzz on about Methanol but at up to less than 10% and I mean “less than,” is what they try do, it will only dissolve the moisture around it.
It’s like a big can of “dried gas” in every fill up!
Moisture will burn just like paint Thinner!
No need to buy more of it or other stuff some scammers are passing off as a injector cleaner for your tank. Too many unknowns of what is compatible down stream to be very harsh!
I might believe in those specialists cleaning them though and in a screen clogging, is about as far as that goes?


Phil

Also, I ran codes and got all clear 1-1-1.

Hey,

How are your IAC hoses? I had a rough missing idle at temp that drove me crazy for a time. Replaced both hoses which were rock hard but no obvious cracks and the problem cleared up.

Hey Carver,

One hose is new and the other probably should be replaced. I'll replace and test it. Most of my vacuum lines are new or newish. It's probably time to redo them all. Thanks, Jim