High idle

Ok I searched and came up with this: http://www.g2ic.com/forums/showthread.php?s=&threadid=39545&highlight=high+idle

But its not enough info for me.

My 91 B18a starts up cold at about 2200rpm, then slowly makes its way up to 3k where it sits even while warm. It has 20" hg of steady vacuum (50cm or mm I cant remember) from the intake manifold, the throttle plate is not stuck open in any way (no throttle cable, and there is same amt of play in the TB as on the teg’s tb), the IACV clicks when battery power is applied, my wiring is right, and the FITV has suction through the hole in the TB (I didnt check if it had suction when warm, its not supposed to). I Screwed the plastic thing in all the way on the FITV and it still didnt help. When I unplug the IACV it goes down to 1500 and fluctuates a couple hundred rpm.

I am getting no codes. I did get a 43 (fuel delivery or something) so I switched some vacuum lines around on the pressure reg and it went away but the idle is the same.

I didnt check the TPS (how do you do that?) yet. Also if I plug the hole the FITV is sucking through should the motor idle down? If it did would it show that the FITV is bad?

Any suggestions?


Ok I did some searching on honda tech (went through 5 pages of stuff) and came up with this info from random ppl’s posts:

"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 varying 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 vengeance to gain some more insight.
Good Day.

Fast Idle Thermo Valve under the Throttle Body. Pull off your intake and while the car is running, cover up the upper left-most hole on the inside of the TB with your finger. If the car dies down and sputters, thats it.

Pull it out (3 10mm bolts) and wrap the top of it in duct tape or duct tape some vinyl. Pop it back on and see if that works…
sounds like my car. i did however THINK i found the solution. First things first. try borrowing an IACV (on back of manifold) from someone. if it stops that’s ur prob most likely. if not. check the voltage readings on ur TPS. the range should be like .450 to 4.5v or near that (mine is way off… .520-4.67 i think). if that’s the case. I’d try a new throttle body. the butterfly might be bent a lil, or u could have a bad TPS. I had this problem for MONTHS and it frustrated all hell outta me. I took it to the dealership. They told me the plate was bent. the guy used to race back in his days so he checked my trunk and found the old nitrous bottle holes (DOH!) so he told me it coulda backfired and bent the plate. I checked the throttle voltage later to find that it was off so that could definitely be the problem. my car doesn’t do it as bad anymore it sorta went away so i’m too cheap to buy a throttlebody hehe. hope this helps.

EDIT: BTW… mine also used to happen after driving fast or being hard on the car (highway runs or sometimes stuck in traffic for hours

check to see if the fuel pressure regulators is working properly. pull the line off the top of the regulator and see if the idle increases or not. the problem may be in this area.

i found it. you are right, i answered my own question. the lower port in the tb was sucking a lot of air and i just had to find out where it was going. as far as the iacv being involved, that was wrong. the upper port (not sucking air) in the tb is associated with the iacv. the lower port (sucking hella air) in the tb is associated with the fast idle thermo valve (just under the tb) which i thought i had bypassed. come to find out, the valve inside it was WIDE OPEN so air was runnin through it like mad crazy. all did was take it apart, screw the valve closed and put it all together. then adjusted the idle with the idle screw and i purrs like a kitten. i will just have to help it along with the warmup process in the mornings."

I’m gonna try this stuff and try retorquing my IM onto the head. I’m a dork and I hope I answered my own questions. If anyone has anymore suggestions let me know.