Good morning! I drive a 91 740 wagon (automatic, non-turbo) and Yesterday i drove about 40 miles on the interstate and the car ran fine. I stopped at a convenience store and when i put my car in park the idle was going up and down from 1000 to 3000... When in gear it seems fine, this morning it was idleing at about 1500 rpm at a stop light. I checked the vacuum hoses and couldnt find a loose one. Just now as i pull into work and put it in park it idled normal... i dont know what's going on... Any ideas??
Greg
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91 745, 85 244 GL

Whap the idle speed motor with the handle of a screwdriver when it's acting up. May be sticking. It's what actually controls the amout of ait the engine is getting at idle.
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cjregensurger@yahoo.com '86, '88 740 GLE; '88, 89 740 Turbo, '88 760 Ti

Yeah, it actually stopped doing it. Now when i crank the car the dash light that says "service" comes on for a minute and goes off. I'm gonna check the hoses when it's not so cold outside. Right now, its like it never happened.
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85 244 GL, Virgos

The Service light is just a mileage reminder (ie. oil change, etc.); nothing to do with specific issues.
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David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near

Hi,

I saw this happen a couple of years ago on a 89 745 turbo, in that case the culprit was a bad fuel injection computer. The computer failed after the car had some body work done, possibly damaged by the welding? got a replacement computer from the pick & pull yard for $35 and the problem was fixed...

Good luck,
JJ

Hi,

I saw this happen a couple of years ago on a 89 745 turbo, in that case the culprit was a bad fuel injection computer. The computer failed after the car had some body work done, possibly damaged by the welding? got a replacement computer from the pick & pull yard for $35 and the problem was fixed...

Good luck,
JJ

Here's what my friend posted back to me about the vaccuum leak:

"The computer on the car when the RPMs are above about 2000 and the throttle
switch is closed will turn the fuel off. Thus when you are going down hill
with foot off gas pedal the computer cuts fuel off saving you money.

Now you get a vaccum leak and the RPMs go high with throttle switch close it
shuts fuel off RPM goes low, then when RPMs gets to about 1000 it cuts fuel
back on. Thus you get a nice oscillation in idle. "

Maybe check your Mass Air Flow connection and wireing. Seems to be mentioned alot here whenever ideling problems develope. The air bypass valve may be sticking. It's under the intake manifold. Take it out and spray some brake cleaner into the end and shake it around until the valve loosens up.

I had a similar problem with the idle control valve. Sometimes WD40 sprayed into the end of it would make it work o.k. for a while, but eventually there was nothing else to do but replace it. Get the Volvo part #off the body of the valve and shop around on line--prices vary greatly. On the other hand, there may be a vacuum leak...

I just bought an 89 760 (mine's Turbo). Same problem. A knowledgeable friend of mine says it *is* a vaccuum leak, and his experience is that the leaks can often be quite invisible on these cars.