Honda Prelude Forum - PreludeDriver.com

Hi guys i'm new to this brilliant forum, i am as of a few months a proud owner of a 92 si srs prelude. It is my first car and it is an amazing car. I am not very good with cars but am wanting to learn how to look after my car. I am hoping you can help me!
Sometimes when i take my car for a drive and then come to lights, or need to pull up for any reason and while it is idling the RPM jumps from about 1k up to 2k, then falls back to 1k and jumps back up to 2k. Sometimes it even goes up to 2.5 or 3k This is a continuous pattern. Sometimes it doesn't happen. There doesn't seem to be any problems while driving, just while idling. I would appreciate any help on this matter!
Thank you

Does this problem happen only when the car has warmed up? If so, this is most likely caused by your IAC (Idle Air Control) Valve. If you're unsure of where that is, let us know and we'll provide more information.

This thread will help:

viewtopic.php?f=3&t=12

yes it does seem to only happen when its warmed up. sometimes it slowly builds up to 2k then drops down to 1k then slowly builds up to 2k, and each time it gets a little bit faster. i just want to know because i had a mechanic look at it and he said that i may have to replace the ecu or some part of the throttle, which i was told could be quite expensive, and dont want to have to fork out the money if it can be fixed expense free..
i checked that link and i will try to do what it says, thanks for the help

Yeah, try what is mentioned in the link I gave you.

It's not your ECU or your throttle body.

i decided to have a muck around and i think its the fast idle valve. i took off the air intake pipe from the throttle body and covered the small hole to the FIV and it seemed to have stopped the idle surging.. now need to fix that

For the fast idle valve, if you just pop the top cap off of the valve body you'll see a (usually white/yellow) plunger on the inside. Sometimes all that is wrong is the plunger has become unscrewed from its shaft. You can use a large flat-head screwdriver to screw it back on.

yes it fixed it and is now running much better thank you very much

Happy to help.

Let us know if you have any other issues with the car.

i have 92 si, lurches and sputters a fair bit when driving, the RPM doesnt change tho.added injector cleaner, no change ... changed plugs..old ones were almost burnt off but had good colour, didnt help...disconnected cat...no change..... could it be plug wires? they looked ok..no cracking etc.... could anyone offer suggestions??? thnx