Hi people! Thanks for looking. I'd much appreciate any help!

My DD, a 940, B230F with EGR, just died. That's the way my Mom explains it. I've got more details:

When I turn it on, it revs high (around 1500) then drops down to about 8-900 as usual. After a short while, it will start "seeking", dropping to around 500, revving to 1200, and back and forth for a while. Often, it will settle around 700 and seem like it's only firing on three cylinders (uneven pattern, shuddering).

While driving, it dies without much warning and without much explanation. Or, it will stick around 2000 RPM even when flooring it, and won't have enough power to do anything.

Tonight I did some poking around, and determined the following:
The MAF itself is perfectly fine. I swapped in a known good from my 240, and the symptoms are unchanged. I put the questionable into my 240, and it runs fine, so the MAF itself is not the problem. HOWEVER, if I disconnect the MAF, it runs steady, can rev up by twisting the throttle, and seems to run just fine, I guess this is "Limp Home" mode. If I plug the MAF back in, it dies.

I thought it was strange that it sounded like it was running on only three cylinders, so while it did that, I pulled each spark plug boot in turn: no change. Then I pulled each injector cable in turn: again no change.

The Check Engine light has been on since I got it. Now with this problem, I finally checked the codes, and it's 121 and 212 (MAF and O2 Sensor, respectively).

Any help much appreciated! I'm pretty handy - I've done timing belts, ring jobs, brakes, clutches, and all such, but prefer not to if at all possible to avoid.

Thank you!

Could a clogged PCV valve be an originating issue for this problem? I did find oil in the air intake, and noticed that the block is "weeping": clear signs that the PCV is clogged.

No, but this points to a significant vac leak. Not definitive, but based on the other symptoms, I strongly urge you to look again. Big leaks are normally where I posted above.

Still, test the O2 sensor. It should swing between something like .1-.9 volts. FAQ's have the procedure.

Well,

I've disassembled, cleaned, checked, and re-assembled the entire pre-manifold intake (PCV, IAC, TB, MAF, EGR).

I found significant crud (not a blockage though) on the EGR entry point to the inlet manifold.

I found heavy gunk in the IAC valve, soaked it in carb cleaner, cleaned it out, then soaked it in oil, then drained it overnight before re-assembling.

I found evidence of heavy oil content in the blow-by: standing oil in the bellow pipe, oil in the inlet manifold, lots of gunk on the throttle body, etc. I also found that the throttle position switch was full of oil, so much so that I thought it may be broken. I took it off of the throttle body, cleaned with carb cleaner, let it dry overnight and re-assembled.

I cleaned all vac hose connectors, inspected all vac hose connectors and other parts.

I cleaned all hoses out with carb cleaner and rags.

The EGR valve itself was quite clean. Side note: why does this car have two EGR systems: one metal running around the rear and entering just after the throttle body, and one rubber running in the front and entering at the filter box? This is my first EGR car.

The PCV oil trap was not clogged! I replaced the o-ring and the flame trap (old one was broken and fixed with epoxy).

I re-set the stop screw on the throttle body and re-installed the (now clean and working) throttle switch. Side question: it has three contacts, but only two of them seem to do anything: the middle and lower contact are closed when idle, and open when accelerating. The top contact does not seem to have any function. Is this correct?

Throttle body gasket and EGR gaskets have been replaced, and anti-seize put on the EGR valve threads.

I checked the fuel pressure regulator: it's relatively new (still shiny!), and no leaks.

I drained the oil and changed the oil filter: when I got the car I had done an oil+filter change and put in conventional oil, and suspect that may have contributed to increased oil in the intake, so I switched back to fully synthetic. As an added precaution, I "rinsed" the inside of the engine with a quart and a half of clean oil and drained that as well, before the filter change.

I also did a coolant flush (well, I didn't mean to: after putting everything back together and starting the engine, I wondered where the puddle of water had come from, eventually traced the water hose above the PCV oil separator... well, long story short, it's all together now).

Result?

No luck.

Symptoms:
Upon startup, it runs fine, revs around 1200 for a bit, then drops to normal idling speed (around 800). Still running smoothly. After a minute or so (not really long enough for the engine to warm up) the revs start to seek: rising to 1000, falling to 700, then rising to 1100ish, falling to 650ish, and continuing like that, in widening amplitude, until it stalls.

For about a minute I can stop it from dropping the revs by pressing the accelerator, and it will rev steadily per my input. When I let off, it will return to the seeking pattern, or it will just drop all the way down to zero.

Sometimes, it will rev up when I press the accelerator, and then drop slightly to around 1200 and run rough: for all the world it seems like it's missing, but it's not. I have tried pulling each plug boot in turn, no change, and disconnecting each injector in turn, also no change.

Next in line: change the fuel filter (it's due anyhow, and I have a filter lying around for it). Oxygen sensors costing around $80 for the Bosch universal, I have to try everything else first.

One other issue: I have to $5 multimeters, neither of which state that they have the required internal impedance (1M-Ohm) to avoid damaging the electronics... so maybe I have to get a new multimeter? Or just get a new O2 sensor? I'm pretty sure it has never been changed.

My backup car: a Ford ranger running on three cylinders and two brakes, just popped the clutch master cylinder on my way home from work: I had an interesting time bypassing the clutch switch with a paperclip just so I could turn it on again and get home. But now I really need my volvo back...

All input gratefully considered! Thanks,

Still could be the brake booster line, check valve or booster itself.

No mention of the bellows check either.

I stand by the vac leak or back O2 sensor judgement.

Bosch universals should be more like $40 is your use the Mustang part number posted here often enough.

I'm wondering, does the engine start surging right away after the cold start, or does it take a short while, say 30 s to a minute or so before it starts?
Edit: d'oh... you already wrote that is does run fine in the first minute. That would indeed point at that sensor as its output is ignored by the ECU in the first minute, when it's too cold to generate reliable data.

The ECU goes in so called open loop mode and relies heavily on the AMM (Volvo's nomenclature, aka MAF) and other sensors to form an educated guess. After that minute it will go into closed loop mode as now the O2 sensor tells the ECU if it applied the correct fuel/air mixture.

You really need to make absolutely sure that there are no vacuum leaks. You checked the hoses, but did you also check the bellows between AMM and throttle body? I read that these sometimes crack in the folds which may be hard to spot.

If that checks out okay then what I would suggest is you get a DMM of at least 10 MOhm input impedance. It doesn't need to be very expensive, but if you already have two, you could check one with the other. Put one meter in Volt mode and hook it up to the other meater in Ohm mode. That meter will tell you the other meter's input impedance. It should prerefably be around 10 MOhms or higher, but I guess 1 MOhms will work too.

Then measure the voltage from the O2 sensor (warmed up). The FAQ tells how.

A correctly functioning warmed up O2 sensor will have an output voltage that you will see oscillate between a lowish voltage and 0.9 V.

A 2-1-2 fault code from the OBD1 would certainly have me check it out.
You may also want to check out this FAQ's list of common symptoms and possible causes and diagnosis procedures.

Good luck!


Oh, about the surging voltage on the O2 sensor. For a threeway cat to function correctly, it needs to do conflicting jobs simlutaneously. Engineers found a way around it by varying the fuel/air mixture between slightly lean and slightly rich continuously. However, this must be within a narrow band around the optimum fuel/air mix.

Interesting times!

I had to drive to the store to pick up a new clutch master cylinder for the Ford, so the Volvo needed to run.

I turn it on, and it runs normally for about 30 secs, then drops into a super low RPM mode; around 200RPM. I guess this is the "Limp-Home" mode. Previously, I had unplugged the AMM when the engine was running, and it returned to idle around 900rpm, so this had me scratching my head. Finally I noticed that the AMM was already unplugged, ok, engine off, plug it in, engine on, wait for it...

And the gremlin comes again! Finally, it drops down to zero, stalls, and I turn everything off. No luck. I thought maybe it would work enough for the short 6mile ride to AdvanceAuto, but now I'm in a bind.

Well, I've read a lot about bad connections... can't hurt to try some contact cleaner... so I unplugged the ECU and the O2 sensor, sprayed DeOx-it (Really good stuff!), let it dry off, plugged the connectors back together, and started the engine.

It runs... idles normally, and I wait for it to start seeking again. It doesn't, so I try to rev it up, and drop the revs.

Each time I release the accelerator, I hear a "Pop", I'm guessing it was backfiring into the intake. This happens two or three times, and I get concerned, so I disconnected the AMM from the air box to try to catch/feel/see it next time.

It doesn't happen again.

After abusing the engine through the throttle for about 10 more minutes, I decide to get to the store.

It drives just fine! I couldn't get it to stall (honestly, didn't try too hard; I just wanted to get home). But it ran quite well.

So... problem solved? I think not. I now have a pretty strong radiator leak, steam pouring out of the hood after a bit of driving, and coolant tank lost half it's contents over a 12 mile jaunt. But I guess that's another problem.

So, fingers crossed, hopefully it doesn't come back. I still have to clear the OBD codes to see if it really fixed the problem, or just postponed the inevitable, but I'm hopeful!

Thanks for your help. I'll definitely check my multimeters against each other.

Well, another short jaunt, and it started again, briefly, then went away.

Symptom: I'm driving (slowly) and all of a sudden the engine stops responding properly: no matter what I do, it won't rev up past 1500RPM, even if I floor the pedal.

If I take my foot off the accelerator, it does the seeking and rough idling as before.

After about 20 harrowing seconds, it kind of cleared up; surged a bit, and then has been fine for the rest of the day.

Bad wire somewhere? This car isn't old enough to have bad wires...

I think I would look for a crack in the Bellows between MAF and Throttle body
--
'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html http://cleanflametrap.com/tony/

Good idea, but nothing there. I know there is a slight vacuum leak in the heater controls under the dash, but it only hisses in one position, and I keep the knob in a different position.

Any work done on it lately? I only ask because of the IAC connector is not unique and can be plugged in to the wrong thing.

So you MAF is guessing what the engine needs for fuel and O2 sensor is reporting how well it guessed. If the two are seriously out of range to each other, you get both codes. This almost always happens when you have a significant source of air post MAF.

Look for cracks in the intake tube, IAC pipes and brake booster line, check valve, or even the booster itself.

The running on three cylinders feel is likely a very lean condition causing one or more cylinders to misfire.

that being said, you still have a serious bad O2 sensor a a possibility but that would almost have to be the heater circuit bleeding voltage to the sensors side.

I see what you mean, but no, this is an entirely new item. I bought this car last winter, and it's been quite good until now. I haven't had to do anything beyond an oil change.

Instructions for checking the O2 sensor can be found in the FAQ's ( drop down menu at top of the page). It involves a meter and back probing the O2 wire looking for varying voltage.

Randy

Thank you! I will have to test the O2 Sensor.

OBD code giving bad O2 sensor... That could be it right there. ???

I don't know the electrical test for the O2 sensor off the top of my head, but that would be my next test, especially if the sensor has high miles/age.

And I have to ask, the MAFs are the same part number?

Good luck.

hi sages- question on the o2 sensor which is screwed into the exhaust pipe on my92 245. car runs fine, starts right up and runs fast and true since 2011. however cel light has been on for 3 years. car has 244k. even gets 25 mpg around town. code says bad 02 sensor. looks like its a wrench out wrench in job. part is 42, dealer wants 850 to replace local indy wants 350. think its a scam. told the code is based on a timer not actual condition of the sensor. fear pc crowd will accuse me of environmental banditry, treason and hurting americas future. uncle moe says to hell with it and keep driving. need to know if my research and instincts are correct from my bruthas on the board who have actually played with this red herring. thanks tons oldduke

Could be wrong but I do not think the CEL light is triggered on a Time basis for this.
The OBD2 codes are more specific then these Volvos but it is possible that there is a Heating Element for cleaning the Sensor and that is what failed. The O2 sensing might be fine. The new OBD2 has separate codes for this heater failure.

--
'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html http://cleanflametrap.com/tony/

Well, after much tinkering, I believe that it was indeed the O2 sensor.

As I mentioned before, I have completely cleaned and re-built the intake, throttle body, EGR, IAC, MAF, etc.

Now I have replaced the O2 sensor and the fuel filter, and the car ran well for a short test-drive.

We'll see if it sticks!