why does my civic rev up and down on its own?? thanks guys

 

Wrong forum, but I'll answer anyway.

Clean the throttlebody and the IACM (Idle Air Control Motor), you've got pcv crud building up near the throttle plate; making the IACM go funky

P

 

Pick up a can of carb cleaner, take the plastic inlet tube off, start the engine and rev it by hand while spraying the cleaner in. The next step, you may need to remove the IACV on the back of the intake. It will be full of carbon. spray it with the cleaner and put it back on.

If that doesn't fix it. On the bottom of the throttle body is the FICV fast idle control valve, there is a plastic plunger on the firewall side of it. It needs to be screwed in and make sure the outer ring is tight and holding it in.

It's been a long time, but I think that should fix the issue.