Okay, so I fixed the a/c, dash noise, radiator, and antenna on my friend's 99 S70 but now a new problem has started.

The car sat for a few days as I spent spare time doing repairs. I did not touch a single thing on the engine as pertaining to ignition, fuel, air intake, etc...

Sometimes the car runs perfectly and idles fine. Therefore, I assume the fuel injectors, fuel pump, ignition system, etc...are all fine. The problem I suspect is with the idle air control system.

When it is having trouble the car will start but the idle will hunt around and as soon as you put it in any gear it will stall. Also, if you are in park or neutral and give it gas to slowly rev up the engine it just fails to rev properly. When you let off the gas in this situation, the engine does not gradually slow down....the revs. just crash down to a few hundred rpm or it will just stall.

I would say 60% of the time the car runs perfectly but the other 40% she is a very sick girl.

Where is the idle air control valve located, how do I test it, how do I clean it, etc....?

What would you suggest doing in this situation?

I have about $800 worth of parts that went into the car so I hate to give it back to my friend with this problem going on.

Help.

 

The IAC is under the throttle cover.
Is the check engine light on? If so pull the codes.