Revs go up and down will cold!!

When a little cold till temp goes to half revs goto 2000 for sec and revs down to 1000 goes this when stopped at a light. When car is warm at half temp stays at 1000. Please help
:2cents:

te hablas ingles???? :p

anyway, if i understand what you're saying correctly, check your coolant level or for any coolant leaks.

When a little cold till temp goes to half revs goto 2000 for sec and revs down to 1000 goes this when stopped at a light. When car is warm at half temp stays at 1000. Please help
:2cents:


check your IACV - take it off (two bolts) use a toothbrush with some carb cleaner and clean the little metal mesh screen - it has a tendancy to get some carbon desposits that can cause this. beyond that - there is also a chance that it could be your FITV (mounted underneath your throttle body) it has 3 bolts to take out in order to get it off - then you can remove a metal plate on the end of it (2 or 3 screws) there is a plastic fitting that sometimes backs off, and can cause a similar issue - just snug it back down (don't overtighten). - try the IACV thing first tho.

cheers and best of luck.

Another way is whith it surging is to remove the intake tube and cover the ports inside the throttle body if the idle returns to normal it indicates that the IAC is stuck open. Also may be a fast idel valve. Depending on the year of the car.

i bought a new idle air control valve and it made the problem worse, i have no idea what to do
-93' SI

i bought a new idle air control valve and it made the problem worse, i have no idea what to do


Hi I tried that also didn't work but check the coolant (sounds simple i know) thats what a user said and yes it was low!!!! now runs like a dream!!! DUMBEST THING EVER

hey i had the same problem with my si the idle would go around 2000rpm then drop down to 100rpm sometimes conk out at the lights till i found the idle screw just above the intake on the throttle body i ajusted it and its been fine ever since.

I have the same problem (if you'd call it a problem) with my prelude.

Searching through past posts helped, but trying to find a definite answer to the problem was almost impossible. The general consensus of people said that it is caused by a dirty IACV (idle air control valve) behind the throttle body.

My own theory, being that it only does it when cold, is that the thermostat sends the signal to the ECU that the coolant is not at proper operating temperature and the ECU ups the idle to heat up the coolant. On the next few cycles, the ECU sees that it's warm enough and lets the car idle down, becoming cool again.

Please correct me if i'm wrong, as this is just a theory. It would, however, be nice to get to the bottom of this cold-weather idle problem once and for all. Seems like some people give others the runaround and/or just recycles second hand information that doesn't seem to work for people in the first place.

hey i had the same problem with my si the idle would go around 2000rpm then drop down to 100rpm sometimes conk out at the lights till i found the idle screw just above the intake on the throttle body i ajusted it and its been fine ever since.


Hi I don't know about your theory but the coolant was the problem for me but my friend had the same problem and had the replace the main power assembly. $30 its a switch which solved his problem. I guess it veries as we have the same year and model lude.