Revving when RPM's below 2000

[Badley]

I have a 2001 Grand Prix with a 3800. Today on the way to work I noticed that when i let off the accelerator and coast the motor will rev when the RPM drops to about 1400 RPM. When it hits about 1400 RPM it will drop to 1000 then rev to 2000 and idle back down to 1400 and repeat the process.

On another note for the last year the car would die when I braked or or coasted in town. I unplugged the Mass air flow sensor and the dieing stopped, but has a harder time starting and a small yo-yo type surge when in park. Today is the first time the yo-yoing happend when in another gear besides park.

Any help would be appreciated. Thanks

[cerick08GP]

IMHO you nailed it on the head, you just didn’t know it. Basically any time your car runs better with the MAF unplugged, the MAF is bad.

[Badley]

Well I replaced it, and it did the same thing. So I kinda thought it wasnt the issue. Guess I can see if i can get it warrantied and put another one in it.

I think, by unplugging it, im forcing hte computer into closed loop. With the MAF plugged in, the car starts great, but dies all the time after the engine warms up, im guessing "opens up the loop" or what ever the terminolgy is. While its running in closed loop it operates fine, until today. Im sure I'm wrong in my thinking, but i figured it must be something other than the MAF. TPS sensor or PCV maybe? I will try another MAF just to see.

[cerick08GP]

Well, it is not unheard of for a new MAF being bad. In fact, I recall a few posts when the correct part was replaced with a “bad out of the box” part. That really can mess up your whole week. You know getting your car scanned is kind of a first step in these sort of things.

That being said, the MAP works with the MAF but rarely goes bad. I’d say it is like a 75:1 failure rate, 75 bad MAFs for every bad MAP.

A bad TPS is a strong maybe.

[Badley]

Ill see if i can get it scanned. I was reading some post about hard start ups being due to carbon build up in the TB on 2004-2008 models. Can this also happen in the 2001's? Or was it something related to the design in the 04-08's?