Our 1999 S80 just started acting strange.

When it first fires up, it idles fine, runs fine. After it warms up, in just a few short minutes/moments - the idle (in park or in gear) bounces up and down (from about 400 RPM to just under 1k) - like its struggling to stay at idle.

Once under-way, it's fine. Runs fine, drives fine, handles fine. But - if I come to a stop and the car is at idle, it's bouncing again - from normal to (what feels like just almost nearly a) stall. It has yet to die when it dips to the low point this idling bounce; but it sure feels like it almost will, nearly will, and doesn't sound happy. Sounds like it's all kinds of struggling to stay at idle.

This only happens once it's warmed up - even just a little bit warmed up. On initial start - everything is just fine. Give it a few moments/minutes, and it goes to idle bouncy. If I press on the gas (while in park or drive) just a little, I get it to even out again and not do the bounce. Like - if I'm in park, and press on the gas just enough to get the RPMs just under 1k (like around 750-800) - it's smooth and behaves like it should.

I *don't* suspect electrical, since I have no lights or indications that the charging system isn't charging - and no matter how much I drive it, the battery stays charged and can start the car just fine.

It *feels* like some sort of MAP/oxygen sensor; that once it gets even a little warm, it's getting mixed signals as far as how much air/fuel, or the idle speed to maintain. Maybe gummed up injectors?

Any ideas where I could start looking, point me in the right direction? This is a new (to me) Volvo - never owned one before, so it's all green to me under the hood. I'm capable to test, replace parts (been working on cars since I was a kid), but any help in the right direction would be wonderful.

Thanks in advance!
-Jason

 

Check your vac lines.

 

Also - in addition to vac lines, clean the MAF (Mass Air Flow) sensor - easy and cheap to do. MAF spray is about $6 for a lifetime supply size can. 2 torx (with the center pin) to get it out and it's right on top the tube coming out of the airbox that goes to the throttle body.

 

Thanks, everyone - good advice. I'll check the vacuum lines and the MAF sensor this weekend (tomorrow). I was just a smidge worried that it might be that ETM module, but when I bought the car the guy had the receipt for the ETM replacement under the recall business - that was done just under a year ago (I've had the car for about 4 months now).

 

If it ends up being the throttle body, I just changed mine over 2 weeks ago to the xMODex model which is a big upgrade from OEM. $549 isn't cheap but it is a fairly easy DIY job.

 

I say it's your ETM for a buck--very similar symptoms to what they do when dirty. Fixed or replaced they always seem to revert back.

Simple to clean, watch this vid.


I've had mine replaced and it started acting up a year later. Cleaned a year ago and it still runs fine.

http://www.youtube.com/watch?v=8Zaxtm-hdyo


Hope this

Kris

 

Ironic that ours started having an idle issue as well -- pulled the intake plenum and cleaned the throttle body and away we go...