I've read about similar sounding problems on this forum, but I'm not experienced enough to tell wether it really is the same thing.

Lots of people have posted problems where their cars idle erratically. My problem is when I'm in first and I give it enough gas to get to 1500 rpm. The car runs normal for a few seconds and then starts to rev on it's own. The rpms go from 1500 to ~1800+ then back down. It causes the car to jerk forward, slow down, jerk forward etc... If i give it some gas and go past 1500 it's fine and then I shift out of first eventually and it runs well.

I've also tested this phenomenon in neutral. If I rev the engine to 1500 it refuses to stay consistent and revs up and down on its own.

My roommate said I'm a bad stick driver (which may be true) and I'm driving it too slow in first, but my foot is on the gas the whole time this is happening so I find that hard to believe. My own research is leading me to believe that it's that whole BAC valve problem; a guy at work also suggested i might have an air leak. I've also entertained the possibilty that the car is trying to tell me "I wanna go faster, idiot."

 

The first thing I would do is check your throttle position sensor (TPS). http://www.fc3spro.com/TECH/HOWTO/TPS/tps.html

 

how does it idle though? forget about stabbing the throttle at 1500...

If you rev it up it neutral - say 4500rpm, then let right off the gas...where does it settle down to and does it stay solid? If its idling fine in that sense it may be something as simple as sticky throttle plates or something.

Also - what do we have here...S4-S5? N/A or turbo?

 

id say tps. i had a weird problem, similar to that, only it happened in neutral. It would just randomly rev 1400~1800 on its own. It was funny because I'd pull up next to other cars, and they'd think i wanted to race....There are 2 ways to test/adjust the tps, and people claim one is better than the other. I find the ohm test to be most accurate, but the light test will tell you a lot as far as a test. I wouldn't adjust it according to the light test. the light test can be found in the FSM, look in the FAQ for links to d/l it.

 

Thanks for all your replies. I will try testing the TPS as soon as I can get a DMM.

The cold start system seems to be working ok. It revs to 3k then drops to 1k or sometimes lower (today it stalled on the first try, but it worked the second time).

If I rev it up to 4500 and let off the gas it drops to about 500 and settles around 700.

It seems like it doesnt want to rev smoothly. While in neutral, I tried holding it at 2000 and it would keep bouncing up to 2500 then drop. It also did the same thing at 3000. Only after 3000 would it rev smoothly.

So do you guys still say TPS?

 

well if it holds idle decent chances are the TPS isn't the culprit....but its worth checking.

Its hard to say....how does it act under load? say you're in 2nd gear at 1500rpm and you apply some decent throttle, will it rev out fine or does it still have the jumpiness?

 

It jumps while idling too. It doesnt seem to do it in any other gears.

 

It's kind of hard to test right now, except in neutral, because I removed the shifter assembly in order to install new bushings (the shifter had a lot of slop in it). I'm waiting of the pieces to come in via mail.

 

Hey just wanted to let you guys know I fixed my problem using the advice you gave me! The TPS was way off, but it was at least working! I adjusted it by following the steps outlined here: http://www.fc3spro.com/TECH/HOWTO/TPS/tps.html

Afterwards, I did a victory lap around the neighborhood... peeled out a few times... you know, drove it like I stole it sort of thing. It was a great feeling. Thanks again.

One thing I noticed though, was a high pitched "circular" sound which I think was coming from the transmission. As soon as I lightly depressed the clutch (like 2 cm) it would stop. Any ideas?

 

Oh my god... someone followed the advice they were given on the first try...

Not only that but they found instructions without asking for a link!

You're my new hero for the 2nd gen forum!

 

^LMFAO +10