2002 s40. 70K miles. Car runs fine except if in very heavy, very slow moving traffic, after 30 - 40 minutes, the car will start to idle rough. Start as a slight shudder and gets worse to where it wants to die. If I put it in nuetral and give it gas to keep it running, the tach will go from say, 1500 where I am holding it up to 2000, down to 1000, up and down. If it does stall, it will start up again. As soon as traffic clears and I get up some speed, its fine. And it will restart and drive fine. There is a real hesitation when giving it gas to get it moving when this happens. Also, rarely, the rough idle will start when starting the engine on a hot start. Only codes that have been thrown are for either random or cylinder specific misfires. Worst (and first) time this happened, the car died and would not idle unless you were giving it gas. We cleaned the IAC and that seemed to sort it out for awile.
Mechanic is trying to rule things out rather than throw parts at it. So far, he's cleaned the maf, throttle body and IAC. Also new air filter and full fuel system cleaning. Overall performance was much better but original problem still occurs if sitting in the heavy traffic. Next thing hes thinking is to replace the IAC.

Any thoughts?

Fuel pump seems good. Doesn't seem like a vacuum leak. FPR?

Thanks!

 

Just one thing to add to my post above.... and I don't know if this is related to my idle problems. Occasionally, if sitting in the same kind of traffic mentioned above, the windshield washer nozzles on the hood will start giving weak squirts or dribbles of washer fluid.

Is there ANY thing about these two things that could possibly be related? Is the windsheild washer system tied into the vacuum system in any way?

 

Hi, have you checked your spark plugs, are they the correct ones?
i had a mechanic install the wrong plugs into mine giving me similar problems to yours, also check the injector seals i had one that was blown. i replaced my plugs, fixed the seal, problem solved..
good luck

v70 2.4t

 

Plugs are OEM installed by Volvo at 45K. Car is at 70K now.... Problem first appeared around 60K.

Hmmmm..... injector seals.....

Can you describe what your symptoms were? And how often it would happen? Like I said, this is only after sitting in heavy NYC traffic for 30-40 minutes and occasionally on a hot start.

thanks!

 

Pull the plugs take a good look around at the leads, test for spark, it won't hurt!! one plug may be fouled. have you checked that yet? , so many idiling problems are atributed to sparkies going bad!!...start with the easy diagnostics first.
My problem was not a severe as you describe, but the idiling was rough
if it's not throwing codes, i would look at spark plugs leads, and all electrical's associated..I would put a fresh set of plugs in, such a minimal cost, and easy to do yourself
Mate i hope this helps!!!
good luck

v70 2.4t