I'm having a strange problem with my car at cracked throttle at constant speed (any speed)...

At light throttle settings, the car bucks back and forth (against the backlash in the drivechain). The only way to get it to stop is to either let completely off the throttle or increase the throttle. Last time I checked the TPS with a scanner, it was smoothe, but have not done so in 2 months or so (and the problem existed back then, too).

I'm thinking maybe a vacuum leak? I'll be looking into that ...


Does anyone else have experience with this problem or have suggestions?

M

 

Check your MAF sensor. I had this problem today at work with an LT1. The guy had installed the MAF backwards. I'm nottrying to say that you're stupid, but your MAF could be toast and not providing an accurate reading.

 

forgot to mention that it may be the IAC as well. Check the voltage on that.

 

Also check the TCC, it may be engaging and disengaging and will give the same effect you describe.

 

I had the same problem 3 different times. Here's what they were:

1st: TPS connection was bad. TPS voltage was dropping to 0 at times!!

2nd: Injectors went bad. Bucked really bad and idled HORRIBLY!

3rd: Ignition coil was arcing badly! Bucked bad again!

Just some thoughts... check the above posts too. Could be alot of different things! Good luck!

 

Same thing happened to me on my non thirdgen.
first time it was 2 bad injectors
second time it was a cracked coil
it's happening again. haven't looked into it yet. too many other projects going.

 

Assuming it's the car in his sig, there's no TC to check.

I'd lean towards a TPS or ignition problem. I'm having the same deal right now on my winter beater. I'll plug away at it; don't want to work on it more than 15 minutes at a time because of the cold.

 

I don't read signatures, some people have sigs 10X longer than most posts.

 

It is, indeed, the car my sig. =)

MAF seems to be reporting reasonable values (not dropping to 0).

I just installed brand new injectors about 2 months ago (Accel 24#'s - yes, I burned a new PROM). They are working great.

IAC also seems to be reporting correctly to the scanner (though that doesn't necessarily mean its correct). I'll pull the throttle body off and clean it.



Could it reasonably be a vacuum leak? Also, I'm reading that this could be a sign of a failing fuel pump (though its been doing this for quite a while now).

 

Would have to be one hell of a vacuum leak, you'd notice it more at idle than cruise speed.
Failing fuel pump, regulator or bad filter is another possibility.