Every now and then I've noticed that my RPMs will climb and hang while I'm driving. It's very obvious that I'm not really at that particular rpm. When I push in the clutch and let off on the throttle the rpm settles back down. Let up on the clutch and the rpms go right back up. Is this an indication of a bad ground? Seems like the tach may be getting a poor signal somewhere. Anyone have a similar problem?



Thanks

Yea, I was just about 2 ask the same question. Just recently my RPM meter started to the same thing. I hope that some the forum experts can help us out https://www.nopistons.com/forums/pub..._DIR#>/sad.png

Does it do this at all the time?

clutch slipping, maybe?

No, it doesn't do it all the time. It just recently started happening. Definitely not a slipping clutch. I can listen to the exhaust and motor and hear absolutely no change and watch as the needle goes up to around 5k and just sits there. If I get on it a little the needle just hangs.... However, when i put in the clutch, the rpms will drop.

So the needle moves, but the eng revs don't change. Maybe just a bad connection on the back of the gauge cluster. Did you install a turbo timer lately? If so make sure you have a good ground going to it.

todd: yep, I've taken a quick look under the dash and there is a nasty swarm of wiring. What would a turbo timer have to do with this issue? BTW, I DO have a really iffy ground for the turbo timer. I just bought the car and haven't had the need to use the timer much so I haven't addressed it. It does seem to be grounding fine however, as I can control when it comes on/off no problem. How would this be related to the tach? Do turbo timers splice into the tach signal?

Sometimes turbo timers use it as a source of how long to say on (auto feature) If you are at high rpms for longer the timer will stay on longer. Disconnect the timer and see if it helps. My turbo timer also has a speed display built into it.

Check your throttle position sensor TPS



It is a big connector on the Upper intake manifold



If it isn't connected this would cause your car to go up to those rpms and really stay there. It sounds like what you are talking about except for that you think it's really not at those high rpms.



Also, check for us to see if this happens when you have the a/c on.



good luck

I had my cruise control cable bind once holding the throttle open partially. Check that.