Hi, I haven't had a chance to check further on this. Thanks for the posts. I'll try all of them including cleaning the throttle body again.

 

Hi all. 1st time user of this forum. Original owner of a 1999 SC1 SOHC manual trans. w/ over 195,000. Same problem as beaverplt. Kinda weird how I just registered to get help with this specific problem only to find another subscriber with the same issue.

I, too, have throughly cleaned the inside of the intake and throttle body w/ aerosol intake cleaner & a toothbrush. I also replaced the IAC & TPS. I did this ~1 year ago when I had a slightly different problem concerning the idle not returning back to 900ish RPM. The idle would stay really high, ~2K RPM or so, and you'd have to try to 'kick it down' by reving the enging even more ... like you'd do to a carburerator. Sometimes that trick would work, sometimes it would make the idle rev even higher. Before I diagnosed the problem, I'd have to load the engine by letting out the clutch partially, just to reduce the RPMs low enough to be able to turn off the motor!! Nice.

Turned out to be the TPS on that one. Of course, the manual lists no troubleshooting for the TPS itself, except replacement. Good thing it was only ~$30.

Now, a little over a year later, the car idles ~1100RPM, about 200-300RPM or so higher then it always did. If I ease off the clutch in 1st gear, she won't stall, rather speed up to ~1800-2000 RPM ON HER OWN!!! Phantom car at its best!

Engaging the clutch fully (to shift into 2nd or higher gear or disengage the transmission totally, as in a panic stop) at moderate speed (30MPH or so) results in the RPM reving even higher, all on its own. Ditto for the racing RPMs when stopped ... however all on its own, when stopped the RPMs will slowly come down to a high idle @ 1100ish. Weird.

Since the TPS was still under warranty, I just replaced it with a new one. No difference. I have NOT recleaned the throttle body, intake, or replaced the IAC. Like I said, all that was done just over 1 year ago.

Now here's the rub ... the only thing different I did - RIGHT BEFORE THIS PROBLEM BEGAN - I changed the battery.

The previous one was almost 8 years old and finally died. So I simply removed & replaced the battery with a brand new one. Then this high idle/reving on its own issue began.

What did I do wrong? I assure you, the battery cables are hooked up to the correct terminals. And the cables are clean, without corrosion, and tight. No crossthreading.

So, what gives? Any help would be greatly appreciated.