I limped home yesterday. Chugged accross the George Washington Bridge in second gear. What makes me think its the air mass meter is the fact that above 2000 rpm the engine was running fine, below that it was sputtering. If it was a fuel problem (fuel pressure regulator), I wouldn't get acceleration at any rpm.

My mechanic buddy says its the hardest thing to diagnose and that he's seen as many as 5 Air Mass Meters swapped out before they got it right on another Volvo. He also says buy a factory and not a rebuilt part.

Anyone have similar experience? This is a 1990 740 Turbo.

Matt

Thanks all for your help!

It turned out to be the fuel pump. I had a feeling it was fuel related and not AMM. I have an extra AMM that is good and they both didn't work and I thought that was fishy. I also have an extra FPR and swapped that out and it still was acting funny.

My mechanic discovered the lack of fuel pressure and voila, that was it...

Matt

I would probably agree, AMM's seem to have non specific failure modes. One failed with a full rich condition (chugging and black smoke) Two rebuilts had a "soft miss"?? under boost conditions. I am presently using my original AMM with almost 375,000 miles on it.
FCP has pretty good prices on new Bosch AMM's.

Of course, with traffic on the GWB you probably didn't hold anybody back! AMM problems, in my experience, manifest themselves in a difficult transition between idle, which will be totally normal, and running, which the engine will barely do. An extra AMM is a nice thing to carry around--I have several spares if you want to try one out and I live in Beacon, NY--is yours the 007 or 014 part number (last three digits)? I think I have both. Otherwise you need a friend with a similar type meter so you can swap. I have never had the experience where one has to go through several to find one that works. And replacing it involves about ten minutes' work--it bolts to the top of the air cleaner housing, which itself is held on by clips, and must be removed from a hose connection at each end. But that's it. Good luck!

Steve

I had an idling/initial running problem...knew that the AMM was a possible culprit from all the board chatter about it. Took the 240 to my decent Volvo oriented shop--they sold me the part for the same price as FCPG--and put it on for $35. They had easily diagnosed the problem with their Volvo computer as being the AMM. How can you beat this compared to all the ignorance and time spent re-inventing the wheel?

Going this route means it's THEIR problem to get a good part in there. Of course, you have to find a decent shop.

I personally think--unless you just get off on farting around with complex stuff in an uninformed way--that you're better off using a good Volvo shop for diagnosis of the electronics and harder stuff, with the option to DIY if it turns out you want to.

Anything else may indicate you don't have enough to do.

Without the good shop relationship, I would say "good luck."