Hi, my old wagon is having some trouble lately... it started months ago with a 2-1-2 OBD code for faulty oxygen sensor/signal. We kept driving as nothing seemed effected by it until recently. It started to idle rough and hesitate slightly for a minute or 2 after startup as if it were a carbureted engine on a cold day. However it is in the 90's and it's fuel injected.

After it "warmed up" for a minute or two it ran fine. However it got worse over the course of 5 days and then it failed to start at all. The exhaust smells of gas and I have been able to get it to start and it just chugs and sputters and then dies when I hit the gas pedal.

It seems to be running rich but I suppose it could also be a weak spark not burning the fuel so I swapped out the coil, cap, rotor, spark plugs, and ignition control module (plug wires are recently new). I also swapped out the oxygen sensor which was covered in carbon (wow is that fun) but still no change in how it runs. Which makes me suspect I'm barking up the wrong tree.

I do not smell or see gas in the FPR vacuum line. I do not see any cracks/leaks in the clean air tube from MAFS to TB. The intake manifold gasket is relatively new and appears in proper order. The TB was recently cleaned, the flame trap has not been cleaned in awhile.

I have not yet done a proper check of the ECT or cold start injector but I wonder if the ECT might be the culprit since it would run fine once it "warmed up". Does the ECT fail in this manner?

Will a failed cold start injector cause these symptoms?

Thanks for your help!



--
'91 240 wagon, '89 240 wagon, '90 740 sedan, '92 740 wagon

I know this post is rather stale, but did you ever resolve this problem?

The shield of the OXS wire (that thick, tough, green one) is grounded at one end, so if the shield becomes shorted to the inner conductor, the symptoms you describe will be present. Such shorts, at times, occur at the end of the wire where the shield is ungrounded.

Rich (near Pittsburgh)

Tough one. First, as Phil suggested, I'd try unplugging AMM and see if it idles/runs better without it. Check the condition of the plug connectors/pins while you are there.

ECT is a possibility. No experience with that bugger!

Yes, the FPR might still be bad. Maybe it just isn't leaking fuel... Test the fuel pressure.

How old is your catalytic converter? Is it original? Have you tested it? A bad cat could also cause rich exhaust. Replacing the oxygen sensor wouldn't compensate for a bad cat. Might explain the excessive carbon build-up though!

Too bad you did not fix the oxygen sensor as soon as you knew it was bad. It does a lot for your car.

You have opened Pandora's box.

Running rich can cause any number of issues.

Our bricks can compensate for many problems, then they give up. Many years ago, I had a new Mass Air Sensor replaced and the tech told me that it may take as many as 12 trips for the car to get the best from the new sensor.

I have used the same dealer for more than 20 years and almost 600 K miles, and I have never had to replace or repair more than one part when one of our Volvos had a problem.

Good luck - getting out of your fix will be a much bigger job than replacing one bad part.

Hi there,

You might be on a good trail as the ECT can cause an overly rich engine response.
If it's unplugged or a bad wire this will cause a false signal or lack of one actually and will make the ECU think its in an Alaskan winter!
Only trouble is, I want to say they rarely fail but that's not never!

There are other things ..... You might have a bad AMM, a leaky cold start injector or still a bad FPR. Especially, if it's not returning the proper amount of fuel back to the gas tank.
Too high of an operating pressure on the fuel rail will provide too much fuel and the ECU cannot trim the pluse on-time length back enough.

A "no volt signal" from the O2 sensor will make the ECU think the engine is running lean but by default, the ECU should not go that rich. That's why you were still able to drive the car so long but not at its top edge (Lambda) in efficiency of fuel economy or emissions performance.

I don't blame you for letting it go!
I know they are overly priced so I use a universal one for $20!
I ignore the stupid ceramic heater inside.
It doesn't take but a few hot licks of exhaust to out strip the time it takes to warm up the sensor electrically.
The other ones, are a consumer rip off! I have seen them for as much as $250+!


If the AMM fails, you end up in a "limp mode." With the key or engine off, try unplugging the AMM. Run it and see if it will idle better but it won't drive off or around worth a darn!

It's sort of a way to check it out but replacing it with a known good one is about the only way to rule it out.
I would advise you to check for corrosion on the both pins or a receded terminal up into the plug side. This causes the AMM to give bad information to the ECU.



You can check the value of the ECT directly on the component. Its hard to get clips down inside the connector end while its under that manifold.
I have a junkyard connector I plug into mine with extended leads I can hook my meter onto.


You might want to search FAQ's for more information on how it is done from the ECU connector.

This will check out the wire coming from the engine and through the firewall and puts things in front of you. It also puts you on your knees so, you can beg for a fix, more comfortably! (:-)

http://www.volvowiringdiagrams.com/volvo/LH%202.4/LH2.4%20ECU%20Pin%20Out.jpg

I found this information above on the pin-out but I'm not familiar of how to interpret the side bar information.
Yours is a '89 so that half of the side note does not apply anyhow?

This other method, expressed in the side bar, must be done with the key on and I assume one must back probe that big thing!
That is what scares a novice like me out of monkeying around with it POWERED and ah-doing some poking from the back side blindly doesn't help!


I use that Bentley resistance reading with the engine off of course, because I can unplug it and peer in there.
I just know it says the pin 13 is the place it drops in.
Going to it with a meter and a "good" ground connection with the other lead, might give you a better overall / continuity resistance reading.


If Art Benstein chimes in, he can shine some of his wisdom on how he does all this!

I bet he has written a post somewhere! Use the FAQ's and ECU & ECT in the same line?

Good luck!
Phil

Hi, all! I just checked in looking for an answer to similar problems I've been having with my '92 240DL. Running rough, inconsistent idle, tends to quit running with any idle time. Pulling bat cable to reset seems to help, but not for long.
Getting the ol' 2-1-2 return code as well. I've had my fuel pressures checked and they're all good. Next step, I think is to change the O2 sensor, but my smalltown local jobber wants $200 for one (CDN, retail), so I ordered one last night on ebay from Global Automotive. NOS Bosch for $US18.00. Trouble is it won't be here for a week, and now to my immediate problem:
I have to go to a wedding this coming weekend. It's a 300 mi. round trip and, although Barby (the car) is running pretty crappily, I'd be willing to subject her and us (her humans) to the abuse in the circumstances if the permanent damage wouldn't be too severe. So question/opinion quest: What would be the problems I'm flirting with, other than possible plug fouling (I'll carry spare plugs) and oil dilution (which I'll monitor). Does this plan make any sense, or do I cancel the reservations and drop the wedding from our plans?
Any advice appreciated in this side-consultation. New O2 sensor will arrive next Tuesday - the day after my (hopefully) return.
tnx,
ps

Well the ECT checked out, replaced FPR and AMM and still no change. Cold start injector and catalytic converter are next...
--
'91 240 wagon, '89 240 wagon, '90 740 sedan, '92 740 wagon

Temp sensor for computor. Extreme richness when faulty.
Check engine timing.

This post that you revived is a year old.

It looks like he went off down another dirt road, that had even fewer sign posts, looking for some exhaust/catalytic converter thoughts on soot problems.

He never came back with more responses so we don't know what fixed it or if it got parked or sold?

Your suggestion is a good one.

Phil

First, make sure the oxygen sensor is getting heated. That voltage comes from fuse 4, so if there's a problem there, you'll get the 212 and no tank pump. The electrical heater is necessary. Then give it a new sensor. A universal is OK if you want to fool with the splice kit in trade for the $$, but anything you might hear on the internet about using an unheated sensor back where yours is... well you heard it on the internet. What can I say.

And when you check for codes, get them all. Don't stop with the first one that reads out. And reset the ECU after you get the codes by lifting out the 25A fuse momentarily.

--
Art Benstein near Baltimore

“The single biggest problem in communication is the illusion that it has taken place.” George Bernard Shaw