Ok, back in March I had the catalytic converter replaced on my '89 240 wagon(had a hole in it.) At the time, the guy said it needed a new O2 sensor as well. Later that evening while driving down the highway the check engine light popped on.

I didn't really think it was a big deal 'cause I figured maybe the guy hadn't gotten the oxygen/fuel mixture adjusted right. So, I had a mechanic friend check it out and he said it was pulling codes that the air mass was off and he adjusted it.

Shortly after that, like 1/2 hour later, the check engine light popped on again.

Meanwhile, I'd been noticing, ever since it first popped on, that the car was not idling well and would sometimes stall at stop or on start up. It has been intermittant ever since.

And, after doing a few more basic things, cleaning the PCV valve, which was clogged and full of oil, etc. the light still stays on (after disconnecting the battery and reconnecting.)

So, today I took it to one of the best Volvo shops in town. I also asked them to do a full diagnostic evaluation, including investigating some oil leaks.

What they came up with was that the air mass meter, air thermostat, and air filter definitely needed replacing. This is what they said was causing my main problem. The codes they were pulling for the check light were all related to these.

This disturbed me because I'm pretty positive that the air mass meter had just been replaced last year by my other favorite volvo shop. But, I told them to go ahead and fix it since I'm just not sure who out of the other people who have looked at the car is being thorough, etc. When I asked the mechanic what could cause the meter to go out in only a year he said that after 30 years with volvo he did not know of anything within the car that could make the meter go bad; it would more likely be a result of the quality of the part, brand, etc.

He also said that my car had an oil leak at the engine rear main seal, and transmission pan needed a reseal. I have noticed some oil on top of the engine close to the oil cap as well as I've had to replace a quart or 2 of oil periodically, and I asked him if this was an indication that there might be something more serious wrong with the engine or the engine cylinders (dad told me to check on this... don't really know what this means exactly.) I asked him if he could check the cylinder pressures, but he felt that at this point that wasn't necessary; that my major issue was with the mass meter.

He also noted that the PCV valve needed to be replaced (the hose was ripped/broken, which I noticed when cleaning it.) I had him do this as well.

I picked up my car and when I got in it the check engine light was still on! I asked a guy to look at it and he checked the codes and said it was pulling from the mass meter and probably just hadn't been reset yet as it was end of the day by the time the work was done. He reset it and then checked the other computer codes briefly and found it all clear. I waved goodbye and drove down the road.

I guess I'd gone about 5 miles when the darned thing popped on again!!! Ok, now I'm super upset! I just paid to have work done that I thought I'd had done last year, and now the light is back and the codes are pulling from the meter! The shop was closed at this point so it'll have to wait till morning to go back. Meanwhile, what is the possibility there's a short in the light??? What else could it be? Everyone who has checked the darn thing since the catalytic converter was replaced (the mechanic friend, the volvo guy, the muffler shop) all have pointed to this air mass situation. Nothing else comes up. What are the odds it's the light?

What does the mass meter actually do and can it be malfunctioning due to some other part malfunctioning???

Is there anything else that could be causing the check engine light to come on, but if so, why is the code pulled coming from the mass meter?

Could the light be coming on from a more serious problem?

Please please help! My instinct tells me that this car is still quite worthy of the work, but I just don't think anyone has really isolated the issue.

Thanks, and sorry for the lengthy message.

Manda