hi there! So I have a Volvo 240 wagon, it's a 1993. It had an issue where it was hard to start when warm after sitting for awhile. Also, it would surge at idle when warm, but not all the time. I ended up finding out that the fuel pressure regulator on the injector rail was leaking (there was gas in the vac hose) and I replaced it. I didn't change anything else and now the won't start when warm issue is gone but now I have the surging idle back, and it happens almost always. When I first start the car, I get a smooth idle, but then it slowly begins to surge, to the point where it's up and down by maybe 200 rpm or more. The way it happens is strange, it oscillates at a fixed interval of a little less than a second, but then it builds in intesity, like a wave or something. I have looked for vac leaks, there are none. I have tested the air mass meter, and it passed the electrical test. here's where it gets more strange. If I disconnect the mass air meter, the surging doesn't happen but it stumbles on acceleration. Plug it back in, and it surges again after starting it up. I also checked the idle air motor. It was clean, I pulled it off and the little door is closed with no voltage and when I apply voltage, the door swings open. Is this normal? The bently tells me that it should do the opposite, closed with volts and open when no volts. I have never seen an error in a bently, but I know it could happen! The only code it throws is 2-3-2, which is compensating for rich/lean condition at idle, or something like that.
I can't figure it out! It runs well driving around. I have a fuel pump relay on the way, just to rule that out too. Any thoughts would be GREAT. Dare I say I'm about to take it to the local Volvo specialist and pay through the nose for a diagnosis. Of course, I'd rather not. :)
Thanks!
Scott

Cleaning the throttle body and making sure the Idle Control Valve is working easily, is where I would start.

I would also take a good look at the Large hose from the Throttle body to the AMM. They can dry out and get cracks in them, not to mention it wears a hole where it leans against the Inner fender well.


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'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.no.net/ebrox/Tony's%20cars.htm

I had an idle surge on my '91 this year that ended up being massive vacuum leaks all along my intake manifold gasket. Apparently it was tripping up the control of the idle air control valve. New gasket - instant relief.

Scott,

Try cleaning the throttle body, then check the operation of the throttle position switch.
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Bruce S. near D.C.

Wow so check this out! I had disconnected the battery just before writing my post and when I hooked it back up and drove the car it runs flawlessly! I had no idea that the computer was that 'smart' or should I say... dumb. Is this normal? I had even reset the 'codes' manually and it still ran like crap until I disconnected the battery and let it sit for a while. I don't know what it did, but wow am I happy to have a GREAT running Volvo back. Thanks for the replies and I'll post if anything ends up happening.
Now, on to the HEATER CORE! YUCK! A 115 mile drive tonight in 30 degree temps and no heat is motivation to get this job done. I need a free weekend and a lot of beer. :)

Scott