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