This only started happening since the weather got cold. Right after I start up my car it stays at 1200 rpms...normal...I'll drive it for about 20 to 45 seconds and then stop at a red light. With the clutch either in or out my engine starts to rev from 750 roms to 1250 rpms simultaneously for about 30 seconds then goes back to normal. I really don't have a clue what it could be but I'd like some info. thnx

 

It's often a vacuum leak. Do you have an adjustable FPR by chance?

 

hey this happens to me too! but mine doens't go back down to normal idle speed,
i've check the fast idle screw, its oke. changed the throtle body gasket. dunno what else it can be?

 

Your IAC valve could be broken.

 

i have 2 iacv for sale...one brand new and one used..for b series motors..make offer..brand new from acura...200 bucks...


[Modified by B18C-RnVA, 8:25 PM 10/6/2002]

 

there is a senor on the bottom of your throttlebody it actually works of the temp. of the coolant. these have a tendency to go out from time to time. replace it. the are about $60 brand new from honda or acura.

 

air in cooling system

burp your system by running your car from cold with radiator cap off for a few minutes. be sure to refill your radiator and resovior later with distilled water.

 

Also could be bad intake manifold gasket.

 

Could this possibly be another reason why my motor is running rich???? my car does it bad too, right when i start it up, (well 5 seconds in) its jumps too, hella embarrassing and annoying!!!! if i bought that 60 buck part, would my car run less rich too, i am runnin good plugs, and my vacuum line is good, (i know cause its practically irremovable since i am runnin a zex kit, and if it comes off its bad news) so i dont know what it is, but my new exhaust is reeeeeeeeeeally black w/ sut.... anny sugg?

 

Just an FYI, this problem is known as "Hunting Idle".

Both the Intake Air Control Valve and the Fast Idle Thermo Valve are fed through holes just prior to the throttle plate in the throttle body. If either of these are allowing too much or not enough air into the plenum, then the ECU tries to compensate to regulate idle. The compensation will effectively over-compensate and you get the "hunting idle" effect.

You can test the IACV and FITV by covering the opening for one of them with either your finger or a well-trusted piece of duct tape. (I will not be liable for somebody allowing the duct tape to be ingested into their engine though.)
Also be careful here because in order to do these tests, you cannot have a filter mounted on the intake system.
As I said, a friend's finger works well. See if the engine will vary it's "hunting" with either of them covered up. (Then test both). As suggested before, any extra air allowed to bypass the TB will confuse the ECU into exhibiting the "hunting idle" problem. This could mean IM Gasket, TB gasket, the Rubber seal on the IACV or the FITV as well. You just have to systematically eliminate possibilities.

This problem has been covered from varrying directions and engines before on these forums. Often people who swap engines will run into this problem(ECU expects one range of voltage from the IACV and the new engine sends another reading.) Use the search method with a vengance to gain some more insight.

Good Day.

 

yea my car does this everyonce in a while.....but it only started after i put on my new intake manifold and tb....an dit only does it on random occasions when its cold...whne i first put the im and tb on it was a lot worse....but i adjusted the throttle cable some and it pretty much went away...now that it is gettin cold again it started doin it a few times again...by the way i do have an fpr...

 

My car will rev-hunt if i hold the accelerator at a point. it revs up and down about 200 rpm. It happened after i put the Zex cam in.

 

Good post. If I rememeber correctly each of the holes represents one of the circuits (can't remember which is which) for the FITV and IACV. If you cover up one of the holes- the engine should die. If it doesn't air is leaking in that circuit, hence bad IACV or FITV. Try removing your IACV and cleaning the small screens of debris to see if this helps. Sometimes the FITV goes bad due to the fact it has a wax plunger and can wear after sometime leading to a hunting idle. Just some suggestions.

 

mine does it too, but only when the engine is cold. Once it warms up its fine.