Erratic idling with AC on

pksarkar · Post by **pksarkar** » 30 Oct 2008, 17:49

Guys,
My 2000 S80 2.0T recently started having erratic idling when the AC is switched on

. Without the AC the idle is steady at around 800 rpm

. Does this point to an impending ETM failure? We just moved to Fiji and bought the vehicle over with us.
There is a volvo authorized service shop around, but they charge an arm and leg to do any work.
Help would be greatly appreciated.
Cheers,

Post by **MadeInJapan** » 30 Oct 2008, 17:57

Welcome to MVS.
It is hard to say what's going on. Maybe it's just as simple as a service belt slipping when the A/C clutch engages? How is the air for the A/C...does it blow cold when it's on, despite the bad idle? I hope others will chime in, but I really don't see how this is related to the ETM.

pksarkar · Post by **pksarkar** » 30 Oct 2008, 18:11

I did check the serpentine belt and it's new.. Also it's not slack. The AC works perfectly and blows cold. With the summer coming in the AC will be used everyday and I want this issue sorted out soon.

Post by **MadeInJapan** » 30 Oct 2008, 19:40

My other guess would be a load on the battery/alternator.
How new is your battery?

Woody70 · Post by **Woody70** » 03 Nov 2008, 11:36

Does the 2.0T have the same brand/type ETM as the sixes? Whenever you turn on the A/C in most cars, something, i.e. a solonoid or vacuum pot on the throttle linkage of older cars, is going to "up" the idle just a hair to maintain idle speed with the compressor running. Seems feasible that an ETM could cause. Since it's completely electronic and has neither of these, a combination of TPS (which is the biggest problem in the ETM) and throttle servo could put the throttle position at just the right spot on the resistor strip where it might be worn through or shorted and cause your idle problem. You might try to use your accelerator pedal to bring your idle up to around 900-1000rpm range and see if it wavers. It wouldn't be easy to keep it steady, but may be worth a try just to give yourself some more ammo for the mechanic. Then there's always the ETM cleaning option posted on the forum. May help, who knows.

Post by **MadeInJapan** » 03 Nov 2008, 14:51

All S80's through '01 had the same ETM. Certainly could be the issue.

Post by **matthew1** » 03 Nov 2008, 16:31

Could just be low on refrigerant, causing the compressor to cycle on/off. At idle this clutch is a noticeable drag on the engine because of low RPMs.

pksarkar · Post by **pksarkar** » 30 Nov 2008, 21:16

Hi Guys,
I checked a few things last weekend while doing the regular service of changing oil and stuff. Took the car out for a spin afterwards and noticed that if I leave the car in "N" or "P" the idling is smooth. It seems only if I have it in "D" that it starts jumping up and down. I'll take it for a AC gas refill. Will update on the outcomes.

Cheers,