Engine revs up and down

When I start the car the idle goes real high for a few seconds. It then settles down but goes from idle to 2000 rpm in a pulsating rythym until you put it in drive. Hard to describe. Is this a sensor problem? The car is a 90 Integra LS.

It could be a vacuum leak.. Or there is another thing that could be wrong. Try this and tell me what happens. Take off the intake piping from the intake manifold and there should be two holes inside the throttle body on the side closest to the firewall. While the car is running plug the holes with your fingers and see if it stops loping. If it runs good I will tell you what you can do that might fix it.

ya i had an accord and i just slipped a bolt in the hole in the throttle body and it quit. (not to sure if its good for the car)

Mine did this one day after I was doing some routine maintenence. Idle was going up and then down. After looking, I had missed hooking the PCV line back up to the intake. Sounds like you could have a vacuum line that came off or is cracked.

Hey JDM, I hope that bolt don't come loose and suck into your intake Manifold. If you look under your throttle body there is a device (i don't know what it's called) it has 3 bolts holding it in. There are two hoses that hook onto it. Unhook the hoses and then unbolt it. Once you have it off take it apart and clean it up real good. (make sure you remember how to put it back together) It may not even look dirty "mine didn't" but lube stuff up and make sure it moves good. Put it back on and it should run just fine. Assuming that was the problem and not a vacuum line.

it's probally just your fast idle

Definetly sounds like vacuum to me. My DSM did that when I first got it and I just re-did all the lines and it ran fine. But that car is long gone now.

it is the iac (idle air control valve)

happened to my car... turned out it was the throttle body, my car had crazy idle hops, from like 1500 up to 2300 and it consistantly did it, than it had little ones like 200rpm hops. hope you figure out the problem and get it fixed

I had the same problem with my OBDI JDM GSR motor. Turns out it was my fast idle located underneath the throttle body. One of the part came loose inside so I took it apart and tightened it back up. Cost me $4 to repair. Needed a new throttle body gasket.

its probably not your fast idle valve, i have the same problem and i bought a brand new fast idle valve and it didnt fix anything. its either your MAP sensor, your TPS (throttle positioning sensor), or your IAC.

TPS sensor = have to buy whole new throttle body ($700 from dealership :gay: )

UPDATE - it WAS the fast idle valve. I took it apart and noticed that the white plastic body inside had loosened up in the barrel. I screwed it back in and the car now idles a whole lot better. Thanks for the tips.

Where and how do you fix this?