98 Civic LX revs by itself! Pls help
 

My 98 Honda Civic is reving up by itself while in park! Yesterday, I put in a fuel injector cleaner right after filling my gas, and got a new battery. This morning it was running perfectly. This afternoon, it wouldn't start, so I tried starting it and giving it a lil gas and after pressing the pedal it started right up, but it keeps reving up and down by itself! When I put it in drive or reverse it just takes off. I drove it 6 miles home and the temp needle went all the way up. Seemed like it overheated. How do I get it back to normal????

Re: 98 Civic LX revs by itself! Pls help
 

See if the radiator is low, then figure out where the coolant leaked out.
Hope there isn't damage form the overheat, but be prepared for bad news.

Re: 98 Civic LX revs by itself! Pls help
 

That would make it rev up and down on its own?

Re: 98 Civic LX revs by itself! Pls help
 

Short answer: Low coolant level can cause it, yes.


The idle speed system must be able to sense coolant temperature in order to control fast idle speed. If coolant is low, then this can be affected. Valve doesn't get heated properly, thinks the engine is cold, opens air passage to raise idle speed.

Excessive idle speed for almost any reason makes the engine surge between 2000 rpm to 1200 rpm because the computer can't control the idle. Has to do with the "decel fuel cutoff" programming....