Thread: GP won't IDLE correctly. MAF sensor?

Hi,

On Thursday I started my 1999 GP GT (125K miles) around lunch time and it would die unless I gave it some gas. It seemed fine on my drive to work that morning. I was in a parking lot at work and my car died 5 times driving around the lot - dying each time I let off the gas. The service engine light was NOT on.

I ended up unplugging the MAF sensor and it would run enough that I could drive to my parts store and get some MAF cleaner. I cleaned the MAF sensor and plugged it back in and it seemed to be working much better and I thought my problem was fixed.

The next morning it wouldn't idle again and just died if it wasn't getting gas. The service engine soon light came on and has been on since. I unplugged the MAF sensor so I could at least drive to work.

The RPMs go up and down when trying to idle, and it dies if the MAF is plugged in. It's not as bad when the MAF is unplugged but it's still jumping around a bit. I just cleaned the MAF sensor again and it isn't any better.

Also, at 4000 RPMs, it misfires with or without the MAF sensor plugged in.

I could post a video to show the sounds and RPMs jumping if that would help.

Any ideas on what I should try next???

**EDIT: I checked the PCV valve and it made a nice clicking sound when I shook it. Next I checked the idle air control valve and messed something up. First of all, one of the two bolts snapped as I was uncrewing and so now it is only attached with one of the bolts as the other one has half of the bolt stuff into whatever it was attached to originally. The IAC valve looked dirty so I cleaned off the cone. I wasn't sure what else to clean or what to use to clean it so I put it back in with the one bolt. I had retracted the valve a bit on accident so then I tried to pull it out a little.

Now there is a sort of LAG from when I press the gas pedal to when the motor responds. You can hear air going in but the engine lags a split second before revving up. Also, when idling, as it jumps from 800-1100, you can hear a "psst" or "pfff" right in the middle of the jump each time it jumps. It is easier to hear if I am sitting inside the car with the door shut.

I rarely do any work on my car and I'm really close to giving up and taking it to a shop.

First, you need to get that IAC bolt fixed. That bolt is a M4 x 0.7, probably about 12mm long. You'll need to extract it and replace it or you'll have a small amount of play in the IAC that may affect its operation. Secondly, to clean it, you'll need to take it out, and spray it down with some Brake Cleaner and use a soft brush or soft toothbrush to scrub it down. Keep spraying it with the brake cleaner to wash away the carbon build up. When you got it all clean, use a small drop of oil on the base of the pintle to lubricate it since the cleaner will remove all oils and such.

Its not wise to ever push or pull on the IAC plunger/pintle as it is a low torque electronic stepper motor that does not take kindly to such things. The hissing sound you are here, while it could be a vacuum leak as mentioned, it could also be from the IAC not operating correctly. Its very possible that the IAC may now be ruined. You can always take it back out, leave it plugged in and start the engine and see if it moves in and out, though that may not be a conclusive test, but it will let you know if its completely dead or maybe not retracting or extending fully.

Next, get you some CRC Electronic Part cleaner from Autozone. Remove the MAF. It uses security torx bits that are also M4 x 0.7, so you will need a security torx bit driver to remove them. Once you have the MAF out, spray the MAF element down with the cleaner and let it dry thoroughly. Then re-install the MAF and see if that makes any difference.

With regards to the misfires, if your MAF is malfunctioning, I would expect misfires. As when the MAF fails the PCM is likely relying on other sensors to compensate that probably are not as accurate nor as quick to respond to air flow changes as is the MAF.

Hopefully this helps out some. Let us know how it goes. Sometimes it takes time to diagnose and troubleshoot things on line, but we will do all we can to help keep you from having to take it to the shop.