Apart from changing the ECU or using an oscilloscope on the fuel injector, I feel like I’ve tested everything else. It was intermittent for awhile, then would get worse when it warmed up, now it idles horrible and when I unplugged the third cylinder spark plug nothing would change, but if I unplugged another cylinder then the car would stumble more and get worse. I confirmed spark but tried different wires, changed the distributor cap and rotor (from another volvo but in way better condition), swapped plugs, swapped fuel injector plugs, swapped fuel injectors from another car, did a compression test which it seemed to pass (went up to 150psi, from 60 to 90 to 120 and stopping at 150ish).

What am I missing? I was so sure that it was the fuel injector, but it apparently wasn’t. It did run smooth once for about ten seconds, when i had fuel injector connector 2 and 3 swapped then started misfiring, and at that moment I could feel the car stumble when I unplugged injector 3. Using the obd diagnostics I can hear the injector click so it’s getting a signal. I was thinking I could take a spark plug out and unplug the spark plugs and turn the engine over and see if any gas flies out of the spark plug hole? I was also thinking I should try setting up my pocket oscilloscope, but I wanted to knows if anyone has experienced something like this first.
Thank you everyone!

Have you tried attaching a timing light to the #3 plug wire to see if it’s sparking in a consistent pattern while the engine is idling?

Hi, I did. I found out the fuel injector I swapped in was also dead, so I tried another and now cylinder #3 works but now cylinder #4 is misfiring. This is leading me to suggest it could even be a fuel pressure problem

Hi,

What about fuel pressure to the fuel rail made it change cylinders?

Nearly everything replaced and it moved so this is a nomad gremlin? (:-)
So this goes with the idea of a “try anything mechanic.”
Boy there’s enough of that going around as we learn.

I think Spook was going with a more logical pattern of thinking ahead than that of my gremlins.

The rear injection clips are more subjected to more heat and water vapor collecting, especially, if the hood is raised in the rain and they are farther from the radiator fans.

Try something like an old TV tuner cleaner concoction and a fiber finger nail file the women use.
Grind the backside of one side away to make it thinner and use it to clean those fine prongs inside each clip.
Same goes for down inside the injectors to give them some polishing up.
Pack the clip with some corrosion inhibitor and it will stay good for a long time.

If the rubber boots on the topside are split then the problem can be deeper on the backside.
The injectors are rated 12 volts but the timing pluses on the coils are very short so just how much actually voltage and current gets around is amazing.
There must be some lag time in those coils losing all it magnetism so wonder just how long the pointless gets to stay shut in reality of being on off anyways.
Are you the one that talked about oscilloscopes and such?
Art Benstein of Cleanflametrap. Com fame, gets into all that stuff. He is my forensics favorite.
Maybe Dave Stevens on the BB too, as he has seen more that 240s and writes out his findings in chats.

Surf here and there for more hints.

Phil

Fuel injector #4 was actually bad, i swapped it with #1 and the problem traveled. I replaced that injector and now I’m in a better place. No one cylinder is misfiring consistently, but it still idle really poorly. I think maybe it is a vacuum leak somewhere. Spraying starter fluid around the injectors causes the idle to improve. So the o-rings or intake manifold gaskets?

Hi,

Yes I think you are getting around to the basic problem of the intake side of the engine.

Having any kind of air entering behind the AMM is going to make the fuel management system to go bonkers. The system is very fast to cover up issues with its adjustments.
Don’t count on computer codes to tell you much unless it falls directly into an emissions program perimeter.

I would start with an intake manifold gasket change.
If you are having the problem move with either a bad injector sealing ring or aged rings it’s going to affect every cylinder intake runner differently. The intakes plenum area, up stream, has its own turbulence factors.
When you pull clips you wiggle them slightly. O rings were all put in as a set, so expect up to a 50 percent failure rate statistically speaking.
Right now you are bumping 25% plus with the less than 50% close by because not every O is identically effected or in a sense, getting subjected to the environment equally.

You yourself might be considered the “unknown factor” causing some differences in the equation.
Humans are really good at doing that everywhere in everything any more.

I wouldn’t be surprised that the intake gasket isn’t in pristine condition if it hasn’t been changed too!
Check the manifold for warpage with a straight edge if it was.
If you are getting a difference with spray over those areas of the injectors, why wouldn’t some of that slip into the intake manifold seams?

You gotta say that some of the simplistic troubleshooting methods do have their ways of earning merits.
I think you are making this project one that you will never forget!
A better mechanic you shall be soon! (:-)

Phil

I just was able to get a fault code 1-1-3, just generally too lean. Still points to intakenmanigold gasket and injector o rings, I replaced the gasket this summer though, I could check if it's loose but it seems unlikely.

While it is not always effective in diagnosing a leaking intake gasket you might try using carb cleaner in your chase.

With the car running spray carb cleaner around the area of the intake gasket. Any variation in engine speed might point to a leaking gasket (the cleaner would act as additional fuel).
--
Any twenty minute job is just a broken bolt away from a three day ordeal

Yep I tried that and noticed some changes. I drove it 45 minutes and now the car dies off i drive it for five minutes. It’s something electrical I think. I got a code 1-3-2 and the fuel gauge slowly dropped from full to empty and the car started dying, with no power whatsoever. Hitting the brakes made the gas gauge drop to zero even. Letting it cool for a half hour let me start it again for another five minutes.

Dear walcyzk,

Hope you're well and stay so. For cars with Bosch engine/ignition management, OBD Code 132 = battery voltage too low or too high.

How old is your car's battery? Alternatively, are the battery's terminals and cable clamps corrosion-free? If the battery is new (or within normal service life) and the cable terminals/clamps are corrosion-free, then we look further.

"Letting it cool...", suggests there's a component, that - when heated - fails. That heat-sensitive part could be: (a) the fuel injection relay; (b) the ignition power stage (Volvo #3501921), which - according to the Volvo VADIS diagram - is on the inner fender wall, just to the rear of the driver's-side headlight.

Check-out these parts. If they are factory-original, they are over-due for replacement.

Hope this helps.

Yours faithfully,

Spook

Hi walczyk,

When your car suddenly quits, does it seem it's running on every other cylinder,
and needing a little gas peddle to keep from stalling. Adding more gas doesn't
result in much more power but too much will stall out the engine?

This is what's going on with my car but it was working for stretches of months before misbehaving again. Now it's in the remission stage.

Is this behavior "Limp Home Mode" ?

I did find somewhere that the Bosch engine management system has a mode in the
program to shut down every other cylinder. In one scheme they use ignition via the
power stage. You can look at this as a RPM governor function.

You might be battling this problem and blaming plugs and injectors etc.

The latest round with my car I found a blown out AMM screen on the engine side,
all those bits of SS wires got sucked into the engine!
I replaced the screen and serviced the AMM connector, and changed the CPS
and the car is back to normal.

I speculate that aging ECU's may be more susceptible to RFI and when I recover
from a shoulder replacement I'll do like Amarin did and replace the old Electrolytic capacitors in the ECU's.

I noted that one of the key engine management sensors the CPS (used to supply
the engine RPM signal) does not appear to have the harness shield connected to
the ground bolt hole. Is it possible that an aging CPU can be upset with
RFI via an ungrounded CPS harness shield? There is a ground wire to the Tranny
bell housing. Check it out carefully.
There is a common ECU ground point by the passengers right ankle.
Two more ECU grounds on the intake manifold, and another ground above the battery.

If it is RFI affecting the the ECU via the CPS harness, you can try adding snap ferrites to the harness, or even easier wrap some aluminum foil around the harness to see if it helps.

I like Spooks suggestions for your intermittent problem, refresh the thermal paste on the power stage, service battery cables and grounds.
Changing out fuel relays can spread open the socket pins. Make a gauge to
confirm that all pins are tight.
When your car quit you could have measured fuel fuses 1 & 11 for +12V to see if it was there or not. put one VOM lead on the cigar lighter ground wire and probe
the in-place ATC fuses from the top where you can get on each side with your probe.

How to unplug an ECU? (this might be subject for a separate post bit it's relevant)
I haven't seen Volvo details for unplugging ECU's, but found that you risk damage if you don't disconnect the battery for 10 minutes before unplugging,
as it is suggested you do when servicing air bags.
I lost an 850 ABS module (ECU) this way.

Also if there's any welding going on in the car, the battery must be disconnected to help prevent ECU damage. When the muffler shop starts welding
do those guys know enough to unhook the battery ground lead?
They're maybe the same guys that torqued your wheel lugs to 800 ft pounds?

You might disconnect your battery overnight to totally discharge/reset your ECU's and see what happens.

Cheers, Bill

Are you setting any OBD codes?

Finally got a code after replacing two noon working injectors, 1-1-3

No codes at all, i might just double check that I swapped spark plugs 2 and 3 and swap them again, i can’t really understand it.

Hi,

Maybe you are moving around a bad spark plug as they can go bad?

The injectors are each powered to ground by the ECU but I think they are wired in pairs so the plus side pins of any clip can be problematic to troubleshoot.
Oscilloscopes sounds expensive and high tech to me.
I have a inexpensive noid light set of four but it has only one that fits Bosch clips.
I Haven’t had to use them much but one of those might help check the clips when wiggling the wiring.

Art Benstein has posted on his web site, Cleanflametrap.com, that on the 240s of them having in-line terminals up ahead of the clips. Maybe that where the pairing comes?
Maybe you have one going south on you and giving a mind twist by just swapping things.

Yep I’m a 240 man and like troubleshooting kept as simple as I can make it too.

Phil

Dear walczyk,

Hope you're well and stay so. Have you swapped-out the fuel injection relay, a.k.a. the radio interference suppression relay? If this relay is "on the way out", it could very well cause intermittent misfires.

Hope this helps.

Yours faithfully,

Spook

Hi Spook,

I discovered the fuel injector I used to replace was also dead. I replaced it again and now the misfire has moved to cylinder #4. Do you think this could be a fuel pressure issue? The worst performing injector getting too little flow? My fuel pressure tester doesn’t fit on the volvo, but apart from swapping the 4th injector again, i think it’s time to test fuel pressure

Dear walczk,

Hope you're well. It is not likely a fuel pressure issue. For, if the fuel pressure were inadequate, no injector would get enough fuel: the intermittency would affect all injectors. To check the fuel pressure regulator, pull the vacuum line and sniff. If you smell fuel, the fuel pressure regulator has failed.

This fault is likely electrical: I continue to suspect the fuel injection relay. The malfunction affects two of four injectors (those on cylinders three and four), i.e., those on cylinders one and two are not affected.

I've not studied the wiring diagram, so can't say for certain that a fuel injection relay failure will produce the symptoms you describe. If the relay is factory-original, it doesn't owe you a penny.

On turbo-equipped engines, the fuel injection relay - if I recall correctly - is mounted on the inner fender wall, just behind the driver's side headlight. It is very dark brown - almost black and is tucked behind a wire bundle, so is hard to see.

The relay could be corrosion bonded to the wiring harness connector, so go gently. If you have an aerosol corrosion-dissolver (e.g., Deoxit), that might help.

The fuel injection relay is Volvo #1323592. If you don't have a spare, it is available from www.fcpeuro.com, see:
https://www.fcpeuro.com/Parts/?keywords=1323592 .

The Volvo-branded part should be available, see: https://www.ipdusa.com/products/22771/Aux-Suppression-Relay-700-and-900-Series-Genuine-Volvo-1323592-141005

Hope this helps.

Yours faithfully,

>b> Spook

Thank you! I hope you are well too. I swapped fuel injectors between cylinder 4 and 1, and the problem traveled to cylinder 1, so I replaced that’s fuel injector as well. Now the car still idles poorly but no one cylinder is missing, if I disconnect any cylinder then the engine gets much worse, unlike before when it was one cylinder that would not work connected or not. I was thinking it could be a vacuum leak now, spraying starter fluid on the injectors seemed to smooth the idle briefly but it wasn’t clear where it was leaking. Starting the car from cold, it idles well for maybe fifteen seconds and then goes bad, this makes me think it could still be an electrical problem.

Hi, and thank you for the reply. It is constant now, and only the third cylinder. Could a relay effect just one cylinder?

my 99 740 has a relay located near the water bottle on the passsenger side fender well. I thought it was black, maybe dark brown? If I pull that thing the engine dies immediately. I dont think it will affect just one injector. in a turbo it will be somewhere else to make more room for the turbo. I know nothing about turbos. I always avoided them just because I like simple things.

I dont know where it lives my 1990 volvo 240 maybe under the floor mat drivers side? there are a couple there one is for wiper delay. I don't know the 900 series too well.

i have a thread open for my 740 ( lost it's mojo) and I'm having some sort of similar issues, my car shakes at idle but runs otherwise.

there is a leakdown test where you might run the engine , let it get fuel pressure, shut off and it should maintain pressure om the fuel rail. I think I had one injector stuck open. plugs looked ok but it would barf up a cloud of white smoke and lack power for the first block every time I got going in the morning. once the cylinder cleared it ran a bit better but I think i was fighting more than one issue at once and that was just one of the problems.

my "poor man with no access to a fuel pressure gauge" check is to say ok it has fuel pressure when I crack the line open I get a squirt of gas from the stored pressure. Even with no gauge I think I can do that after 1/2 hr or an hour after shutting it off and I should still see some pressure. I'm not sure how long it should be expected to maintain pressure when all is normal. all I'm saying is that when you crack the line you can tell if there is pressure by the squirt ( or no squirt) it won't give you a pressure value of course.

If you pull the plugs try sniffing them and see if they smell like gas. I seemed to find #3 smelled like gas.

check under the right year, model etc but those O rings are cheap and there are some other parts you can change on the injectors for not too much money.

https://www.rockauto.com/en/catalog/volvo,1990,740,2.3l+l4+sohc,1288425,fuel+&+air,fuel+injector+seal+/+o-ring,13679

note that there seems to be two kits there.. , one has that pintle cap, and some o rings and a yellow ring there is another ( kit) there that seems to contain a white fine mesh plastic screen filter and I haven't taken them apart that much but I think you can change the filter. I found a youtube on taking them apart. I think if you connect 12 V they open so that may be a part of the cleaning. there is a fine needle in there you have to be careful with.

I think it helps to put oil on them to install the rail. I think you can also drip a couple drops of oil near the seals with it running and if the engine is able to suck that oil up then it's leaking there. I pulled a rail from a car and they were like rock and I had a hard time installing the rail. I think you can bend it where it mounts if you aren't a bit careful and then it might not push down just right when you tighten up the bolts. I found it helped if I get a flat screwdriver between the plates right where the 2 ( 10 mm head) bolts go and pry a bit there while pulling it up.

best to be prepared with new O rings at least if you pull the injectors out since they are cheap.


oscilloscope , I have one and if you do not here's a suggestion. If you have a old computer with a sound card there are software programs you can download for free and install , then you can use the sound card inputs to feed the scope, It gives a good display and will function. ( just search for oscilloscope downloads)

on the probes you can probably add a high value resistor, like 1 meg, that won't allow a lot of power through, also you can use a small non electrolytic capacitor to prevent DC transfer ( capacitors block DC but allow AC to pass) maybe about 5 microfarads is ok.

the cap will block DC but allow AC. this may help isolate and protect the sound card if you happen to probe something with more voltage than the sound-card can take.


if you have an old workstation type computer from bygone days, than you might be able to use that and not risk your decent computer stuff, just in case..

I don't doubt there are cell phone apps and modern things but I tried it some 20 years back with an old computer pentium 2 or something of the era, and found that works well then you have a free O'scope.

lets not be confused because Phil was helping you and myself on two separate threads. my name is phil as well , Ill stick to amazonphil to avoid confusion with the other Phil. He helped us both a lot recently.


amazonphil

Dear Amazonphil,

Hope you're well and stay so. The relay to which you refer is the "radio interference suppression rely" also known as the fuel injection relay. See my posts for suggestion that this be replaced, if it is the factory-original item.

As to your car shaking at idle, have you inspected the idle air control valve (IACV)? It is mounted below the intake manifold. These get dirty over time. See the FAQs for the cleaning procedure.

Hope this helps.

Yours faithfully,

>b> Spook

I didn't want to confuse this thread but there seems to be some similar symptoms to my thread ( 740 lost it's mojo)

I did try swapping for a used idle control valve and basically rinsed it out with carb cleaner. I dont think it's functioning and need to delve into why so I should check power at the connector and maybe I can just connect it to 12 V and see if it opens or seems stuck.

my engine runs but it shakes at idle to the point where its' not good to drive right now.

I blew an ECU once before by mistakenly getting my charger cables swapped around, lesson leaned. I ended up buying two 740's to have parts onhand so I have spares now.

I did try in my 88 van which has a bosche ECU that looks very similar, I clipped the caps just above the board and got new caps. I wrap the new leads around a pin so they are spring shaped and slip over the little leads I leave by cutting the old cap about 1/8" above the surface of the board. then solder

I found it not hard to swap them without taking the board out of the aluminum case and replenishing the heat transfer compound. if you try this first look for the band on the cap indicating negative and put the new part the same way , polarity does matter here.

in that case I made a little slip up and clipped a corner off a transistor and just replaced it with a rebuilt ECU after I did that but that seemed to make a difference on how the van idled.. I think I should try the same on a volvo ECU and ICU and try swapping them after changing those caps, The small 16 V electrolytic caps themselves are cheap parts. I think in my van they were around 3 or 4 microfarads but I'd check and replace with what's on the board. I think there were 3 in the van's bosche ECU, the volvo is likely similar.

I have a feeling that my car is shaking so much because it is running in limp mode, unplugging the idle control valve seemed to not affect it's idle so that's why I think its not functioning. the reason for it not functioning I've yet to solve

I recently has idle issues and bad performance on both my 88 740 as well as My 1990 240 ( both have b20 F engines) I found that both cars were improved dramatically by swapping air mass meters from other cars of the era. it was previously noted that the air valve on the air filter box gets stuck and causes the hot air to come from near the exhaust manifold even when warm, and this may affect the longevity of the Air mass meter. they do fail and I dont know of a way of testing them other than by swapping for a known good one.

The ECU mass meter and ICU are all a bit expensive which is why I bought spare cars, however the caps may fail after 35 years anyway so older parts may not be as reliable as new or rebuilt.. It may be simply that the caps fail and not the rest.

my brother successfully converted 3 of them to carbs and ditched all the electronics so I got some spare parts that were left over and that's been handy for swapping. 240's from the 80's had carbs and they were a lot easier to maintain than this complicated system, some power loss , but it definitely increased reliability. he left the prepump alone and installed a lower pressure fuel pump and pulled the ICU and ECU. I'd love to swap for a couple of SU's like my 122 has.
You need a older intake manifold and carbs and a fuel pump that's appropriate and a points or earlier distributor. I stuck a 74 distributor in my 122's b20 and the control box to get electronic ignition. you can use a points distributor. some engines have a distributor at the back of the engine and that might need to be removed or simply disconnected. I think they still have the gear on the cam to drive the old style distributor.

amazonphil

Dear amazonphil,

Hope you're well. When was the last time the timing belt was changed? The violent shaking may be due to the belt having slipped a tooth. That disrupts the timing pretty severely.

Timing belts have a 50,000 service life. They may go for more than that, but that's "borrowed time".

Pre-1993 (up to and including 1992) B230 engines require a timing belt with "square" teeth. Post-1992 B230 engines take a timing belt with rounded teeth.

Hope this helps.

Yous faithfully,

Spook

Thanks Spook, I'll check the belt out. It i one thing I can verify and take out of the picture.

rather than bother or "steal" this 940 thread by interjecting within it too much, Ill just start a new one and reference my " 740 lost its mojo" thread which also got quite long and wordy. I'll try to condense it a bit.

appreciate the help and suggestions.
Amazonphil