Uneven accelleration, tremble when driving.

[guitarfish]

I have an '02 GP with the 3800 engine. I'm trying to diagnose a hesitation/tremble when driving.

When I step on the accellerator, it's perfect - smooth accelleration, smooth shifting, etc. However, at easy, drive through town kind of driving, there's an unevenness to the accelleration, it happens in all gears.

It's actually been doing this for over a year, I've never gotten serious about it. I do know that I've changed the spark plugs & wires, fuel filter, PCV valve and air filter over the last year, and none of these have made this problem better or worse. There's no SES light tripped from this either.

I know it could probably be 20 (or more ) different things, but thought I'd just through this here and see what ideas people have.

[richtazz]

Sounds like what they call chuggle or fishbite. Many forum members have cured the problem by unhooking the battery and leaving it overnight. For some, it's been a permanent fix, for others not. It it continues, you may have a PCS or shift solenoid problem in the transmission.

[guitarfish]

Thanks Rich...just seeing that as I search other posts. I'll give it a shot, thanks!

[Thorn71]

i am thinking vacuum leak, leaking injector or bad throttle position sensor aka ....TPS.

[guitarfish]

Good news! I disconnected the battery overnight, and voila - the car runs great!!! No more "chuggle". At first I couldn't believe it, but it's really gone. I've had this problem for well over a year.

Now this prompts more questions...

-How long will the "fix" last until the chuggle comes back?
-What causes this chuggle thing to happen in the first place?
-Does GM have an explanation of this behavior?

Thanks everyone,

-Dave

[richtazz]

I know of a couple of cases where it's been a permanent fix (so far), and a couple that it worked for varying amounts of time, then the problem resurfaced. None of us are sure why it works, it just does.

[guitarfish]

Oh well, disconnecting the battery overnight "fixed" the problem for about 10 days, and now the chuggle/fishbite is back. What a pain.
Not sure what to try next.