I took the car this morning to get a new down pipe installed on the 245, since the old one had a hole in it. While the new pipe was going on, I had my exhaust guy take a look at the catalytic converter. He indicated that there should be way more honey comb catalyst inside of it and that what was left was 50% blocked.

Went ahead and had a new cat installed. Thing is running better with more power on the highway. However a check engine light immediately came on while driving home.

Pulled the diagnostic codes and they are:
2-2-1 Fuel system extremely rich or extremely lean air/fuel mixture at cruise
2-3-1 Fuel system compensating for rich or lean air/fuel mixture at cruise

So what now guys? The idle is pretty good. I'll check to make sure all the spark plug wires on on tight.

I guess I'll check the oxygen sensor for kicks.

I'll also look for more vacuum leaks and flip in a spare AMM and Fuel Pressure Regulator.

Tom
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1992 Volvo 240 & 1998 Volvo C70

I went to the junk yard and spent $15 pulling an oxygen sensor, Volvo accordion intake tube, and fuel pressure regulator.

I installed them this afternoon and the car seems to be running ok. No check engine light. Car seems to have more power and seems to not be missing.

I double checked the distributor cap connections and discovered that Jr. didn't push the spark plug wires down far enough on the cap connections.

Jr. will continue to drive the car to school this week and we will see how the gas mileage goes and see if the check engine light returns.

Tom
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1992 Volvo 240 & 1998 Volvo C70

Still not fixed.

I'm out.
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1992 Volvo 240 & 1998 Volvo C70

Looking at the FAQ I found the oxygen sensor wires in the engine compartment.
I pulled the rubber boot up over the single wire spade connection. The sensor connects to a green wire in the harness of the car.

I measured the voltage there and it was bouncing around. Max was around .79 volts. Minimum was around .1 volt.

I made a vacuum leak and the voltage dropped below.2 volts.

I also looked at fuse #4 and it seems good.
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1992 Volvo 240 & 1998 Volvo C70

I also pulled the vacuum hose off the fuel pressure regulator and plugged it with my thumb.
The oxygen sensor voltage went up to .9 volts and stayed there.

So the oxygen sensor seems to be passing the Bentley manual tests.

I swapped in a spare AMM for kicks. Might be running better, but the problem seems to be intermittent.

Another step closer to selling...

Tom
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1992 Volvo 240 & 1998 Volvo C70

Hi Dan,

Regarding the "missing signal" code, test your sensor as in the youtube video below. By putting it in a flame it could burn some of the carbon deposits thus clean it at the same time. And if there is loss of signal during testing there could be some fault in your sensor's wire. Less likely but its possible.

See:
https://www.youtube.com/watch?v=YL6xkOZxHZ0

As you mentioned the problem is intermittent. Another possible cause for "missing signal" is intermittent exhaust ground. Test its ground to engine especially when the CEL is on. It should be below 1 ohm. The sensor uses its body as ground. I suspect that after your recent exhaust replacement there might be some ground faults too. Again, its less likely but possible.

Regards,
Amarin.

Sensors get old and slow . You should see at times over 1.0 volt. If you never changed the sensor???

The oxygen sensor was replaced 37,000 miles ago.
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1992 Volvo 240 & 1998 Volvo C70

The code that was set comes from when the oxygen sensor was not being seen at all. That happens when the voltage does not budge from 0.5V, which comes from the ECU and not the sensor. But your sensor is working well now. That is the behavior of a loose connection. Amarin makes one good point -- that the exhaust pipes provide the sensor's signal ground path back toward the ECU. That was the big reason car makers added a 4th wire soon after these cars were designed. If you have rust, loose exhaust pipe joints, the OBD may have caught the condition to set the 212 code. Then you warm it up and the metal makes better contact, or a bit of movement scrapes off the rust.
--
Art Benstein near Baltimore

Advice for the day: If you have a lot of tension and you get a headache, do what it says on the aspirin bottle: "Take two aspirin" and "Keep away from children."
(Author Unknown)

Drove the car again.
Check engine light came back on.
Codes:
2-3-2 Fuel system compensating for rich or lean air/fuel mixture at idle.
2-1-2 Oxygen sensor signal missing or faulty.
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1992 Volvo 240 & 1998 Volvo C70

After the cat was replace, was the O2 sensor wire checked for connection. Your code suggest this ( No signal)

First, lift fuse 6 for a moment to reset the computer and see if the codes or the CEL returns.
--
Art Benstein near Baltimore

I never drink water because of the disgusting things that fish do in it. - W.C. Fields

Thanks Art.

I pulled fuse #6, waited a minute, then put it back in.

The car doesn't want to run, it sounds like it is missing and about to stall all over again like it did last week.

Tom
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1992 Volvo 240 & 1998 Volvo C70

I left the car running while I posted that last message.
The idle has now smoothed out.
No check engine light yet.
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1992 Volvo 240 & 1998 Volvo C70

Check your engine temp sensor as this controls the start-up mixture. Do a basic test on O2 sensor. How's the air filter?