whoa i got this problem with my car, it likes to rev itself hhehe like every once in a while....it goes up and down and up and down...like a rough idle...anyone experience this? and how do i fix it? i own a 90 vert non turbo. byt he way this only happens on idle not while i am driving...ooh and also at stops waiting for light to turn green.

Fred:P

 

This is usually either TPS or vacuum leak. Slightly adjusting the idle screw may yield some results, but thats not the issue (I think....). Gotta check the TPS around idle and check all the little vaccum hoses....

 

Does it go from normal idle 750 and drop to 5-550 and return, bouncing around every now and then? If it returns back to normal idle and keeps it occasionally, it sounds like the TPS.

TPS=Throttle Position Sensor

In most cases all it needs is adjustment, in other cases, replacement.

 

Definately the TPS or a vacuum leak. I had the same problem when I first got my car. Tried to adjust the TPS and had no luck. Turns out it needed to be replaced. I also had a minor leak which was easily corrected. Now, the car runs beautifully.

 

what about the bac valve. i have a safc and it shows 0% throttle when that reving thing happens to me and i dont have any vacuum leaks.

 

i guess ill check into that tps think in my manual...hope i dont need to replace

 

I've also heard that grounding your engine to your chassis can help. I also have this problem(intermittently), and I was told grounding the engine might solve it. I haven't actually gotten around to doing it yet, but when I do, I'll let everyone know if it ever worked.

 

I had the same problem. I adjusted the idle screw and the problem went away. Haven't had that problem since. But when the weather changed, the idle stays at around 2500 rpm, and then gradually drops to 1500 rpm. Is this becuase of the change in wheather, or is it something else?