2002 4cyl idle problem with AC on

[DavidBo]

I just replaced the battery on my 2002 4cyl Vue. Since then I noticed that the idle surges wildly, almost to the point of stalling, whenever the air conditioner is on. No problems at all with the A/C off. I know that after a battery replacement there is a period of time required for the computer to 'relearn' everything; but it's been almost a week with no improvement. I did an online parts search for an idle control valve with no luck, so I don't know if it even has one. There are no aftermarket tech manuals for this car which doesn't make troubleshooting any easier. On a side note I did notice a good bit of oil under the AC compressor last time I was under the car, but the cooling is fine. How big a job is it to replace the compressor? Thanks for any advice...

[fdryer]

You may be describing two problems that have to be separated. Try disconnecting the a/c compressor power lead that goes to the compressor coil. It should be on top of the compressor in plain sight. If its disconnected and you turn on the a/c you shouldn't feel any cooling or hear the distinctive clicking of the compressor clutch engaging to verify the power lead was disconnected. At the same time this occurs you may or may not see/feel/hear the engine surge as the compressor isn't loading down the engine. Normally the idle air control valve (can't find it in rockauto.com's listing) will readjust the idle speed to make up for the load the compressor places on the engine but since there isn't any power to the compressor clutch for engaging the compressor to the serpentine belt system the engine speed change isn't detected and there shouldn't be any surging at all. If the surging disappears from disconnecting the a/c compressor then the compressor may be failing when power is applied to it. The oil leak may be a hint but you must be sure of this by looking again and feeling around the compressor body, especially around the rear case or front pulley area where the front seal resides inside behind the compressor clutch. A large amount of oil that can't be traced to an engine oil leak would most likely be from the compressor or any part of the a/c system. Looking carefully you'll notice that the a/c system plumbing is made up of high pressure hoses and aluminum that will flex over time and eventually weaken into a stress crack that allows refrigerant and refrigerant oil to leak out. The refrigerant oil is the telltale indication of an a/c leaking but your eyes and hands will tell you where and if there's a leak. If the compressor has oil all over one end and the idle is fine with the power disconnected to the compressor you can try re-connecting the power lead to the compressor (the a/c should be on before this re-connection). If the idle surges again then it may be a compressor failing from lack of oil lubrication even though the cooling is adequate. Its just a matter of time before the compressor loses enough oil to seize or the refrigerant leaks out to stop the compressor from running anymore through a low pressure switch that disables the compressor from further damage.

Compressor damage should be investigated to find out why it failed before replacing it. Replacing a compressor won't be a simple remove and replace as there are several pieces of refrigeration equipment needed to complete the repairs. You may be able to perform the removal and replacement but not the evacuation and recharging without the equipment. This may be better left to the local a/c repair shop keeping the costs down. You'll still have to replace the O-rings and refrigerant oil or at least give as much information to the local repair shop for them to estimate the amount of refrigerant oil to put back into the compressor. Usually draining the oil from the old compressor is the amount of new oil placed into the new/rebuilt compressor that comes empty. A new compressor with oil has to be drained and only the amount drained from the old compressor is the amount used to refill the new compressor. Too much oil leaves little room for the refrigerant. A large oil leak may require more thought. Do you understand what you're getting involved in as a/c repair is no small feat? Here's some background info; http://www.saturnfans.com/forums/showthread.php?t=80107

On the other hand, if the surging continues w/o power to the compressor and the a/c is on then the iacv may be the problem. Removal of the iacv from the throttle body is necessary to attempt cleaning with electrical contact cleaner before trying it again. If this fails to correct the surging then the iacv needs replacement.

[scys]

Is there any surge when the fan turns on? My idle drops a little and then goes up again every time the fan turns on and also with the AC. Mine is an 02 as well and has done it since I owned it.

Cy