Hey all!
I noticed the idle was dropping to 500rpm when I would come to a stop, but then it seems to pick back up after a few seconds. I took this as it needed a basic tune up so I replaced all 6 coils with new Lucas ones, and 6 NGK iridium plugs. I also noticed oil was filling the plug holes. So I replaced the valve cover gasket and the spark plug gaskets. I’m still noticing the RPMs dropping when coming to a complete stop. Am I missing something here? Fuel filter was changed about 30k miles ago as well. Any advise would be greatly appreciated! Roughly 162k on the odometer.

 

Mine did that for along time, intermittent, cured finally with new fuel pressure valve under the bonnet/hood
also clean your MAF with airflow meter cleaner

 

Thank you for the tip! I will give it a shot. Do you have a location where it is under the hood?

 

If you have the AJ16 engine, you might have done yourself a disservice with iridium plugs. People seem to have issues with non-copper plugs, typically the Champion RC12YC, or NGK BKR5e are consistently successful.

As for the coils, Made In Japan by Diamond branded coils seem to provide the OEM longevity most drivers desire, however QYL on Amazon have gotten rave reviews, and at that pricepoint, who would argue? The others seem to start failing between 6-12 months of use.

Lastly, your idle issue is likely a gummed up throttle body butterfly. It isn't difficult, or expensive to get in there and clean it out with a can of carb cleaner and a rag or two. The best way to do it is to take the throttle body off and clean it from both ends.

 

One issue that has been associated with falling idle or stalling when slowing to stop or turn is low transmission fluid, so as counterintuitive as that may seem, it's worth checking your trans fluid while hot from a good drive, parked on a level surface, engine running, after holding the brake pedal and running the gear selector through all positions, holding each one for at least three seconds to fill the valve body. The transmission fluid should be exactly at the HOT line.

Another possible suspect is the idle speed control valve, which is part of the throttle body. Don't attempt to remove the stepper motor to clean the gunk out of the valve without studying posts on this forum that explain techniques for removing the screws without breaking them.

Cheers,

Don

 

I would echo precisely what Don B said. If you have a normally aspirated car, it is relatively straightforward to remove the throttle body to clean the butterfly and idle air control valve, but if your car is supercharged, welcome to a world of pain! In either case, it is well worth reading the various threads in here as there are a few pitfalls for the unwary which are best avoided.

 

Don B is correct, it can also be the IACV.

I'd still start with cleaning out the throttle body...and while you're there, spraying some MAF Cleaner on the MAF sensor.