Idle

[tmracing83]

So what's causes a car to idle high at start up (up to 1500rpm) but once it's warm up from just driving say a mile or so it's down to normal (750-850rpm)? Also how would you go about fixing the problem, I'm betting it could be more than one thing cause this like always.

[aaronfelipe]

I found this from doing some research:




The idle on our Hondas is a tricky thing. It is controlled by two main sensors: the FITV and the IACV. The FITV is a mechanical valve that is controlled by coolant temperature (there is no ECU plug to it). When the coolant is cold the valve is open and letting air into the IM through a hole in the TB before the throttle plate. This essentially creates a small vacuum leak which in turn lets the motor idle higher than normal (supposed to be around 1500-2k for warming up). As the coolant warms up the valve closes and no longer lets air in through the hole in the throttle body. All the while the IACV, which is ECU controlled, is letting small amounts of air into the IM through another hole in the TB. Any amount of extra air the ECU is not expecting will confuse it and you will get either a high idle or a roaming/hunting/fluctuating idle. On to the troubleshooting.

First things first, don't skip any of these steps. From what I have read (and experienced) usually small dumb things cause these problems so don't overlook anything. Also refer back up to the pictures if need be.

1) Check your vacuum routing. On the underside of your hood there should be a vacuum diagram. If there isn't a diagram under there, there is one in a Helms, Chiltons, or Haynes manual for your car (you should have one of these anyway). Remember, ANY extra air will confuse the ECU. Check for cracked or bad vacuum hoses. If in doubt just replace the hose, they are cheap.

The PCV valve could also be the culprit. Take it out and examine it. If it is cracked it could be causing a vacuum leak. Replace the peice if you arent completely sure it is ok (the helms/chiltons/haynes manuals tell you how to check it).

2) Check to see that your throttle plate is closed all the way. Take your intake off at the TB and check to see that nothing is blocking the plate. If nothing is in the way and it isn't closed all the way, loosen your throttle cable.

3) Check to see if the nuts holding the TB and the IM on are tight, this was the source of my idle problem. If they are loose, tighten them.

3.5) Check the Idle screw. Its on the top of the TB right next to the red vacuum line in the first picture. Its a flat-tip screw and most TB's have it epoxied over. If your screw is not epoxied over try adjusting it.

4) Bleed your coolant. Some air bubbles may throw the FITV off and keep the valve open.

5) Take the 3 10mm bolts out of the FITV (you don't have to take off the coolant lines). Then take off the 2 8mm bolts off the plate on the back of the FITV. Once the plate is off you will see a white plastic thing, screw that all the way in. This causes a TON of people's hunting idle problems (it's a source of a vacuum leak). Put the FITV back on and start the car up. If it still idles bad go on. Here is a writeup on the FITV.

6) Clean the IACV screen(s). See Oz's write up on G2IC.

7) Make sure your car is completely warmed up. With it running, take the intake off the TB. There are 2 holes right in front of the throttle plate, these are the holes that feed the IACV (top hole) and the FITV (bottom hole). With your finger, cover up the bottom hole (it should NOT be sucking if your car is warmed up). If the idle goes down the FITV is to blame, either get a new one or take it apart and screw the valve completely closed (I have only read of people doing this, so I don't know exactly how. Also, you will have to keep the engine speed up yourself when the car is cold).

Next cover both holes up with your fingers. The car should sputter and die (or almost die). If it does then the source of your crappy idle is the IACV. Replace it. If you want you can test the IACV. Shut the car off and put + battery voltage to the blk/yel terminal (on the valve) and momentarily touch ground to the blu/yel side. When doing this the valve should click, if it doesn't, replace it.

If, when covering both holes the car still has a high idle, you have a vacuum leak somewhere. Again check the IM and TB nuts. You can spray carb cleaner around those areas and if any gets sucked in (the engine will rev) you have found your leak. Another source of vacuum leaks are where the FITV and IACV connect to the IM. Either replace the gaskets or use silicone gasket sealant.

8) If nothing has worked you should test your TPS. Probe the middle wire on the TPS plug (with the key on but not running, and the plug still connected to the sensor) with the + probe on the volt meter, and the neg probe to ground. You should have .5v with a fully closed throttle plate and 4.8v with it wide open. If the TPS is off, replace it. My TPS was .425v to 4.55v and it idles fine now so I don't know how big the margin of error is. Also, it is pretty rare for these to go bad.

9) If, still, nothing has worked you might want to try a new ECU. This also is very unlikely, but worth a try.

10) If it still idles bad, go through the steps again.

It was a pain to have this mysterious problem and very little info on how to go about troubleshooting it. The idle problem is a real PITA because there are so many things that cause the same result (the hunting idle). When I had this problem I read through a ton of posts over at Honda-tech describing the exact same problem but when I PMed them, they all had different fixes. I hope this covers all of the possibilities. If I skipped over anything PLEASE let me know.

[Barefoot]

I found this from doing some research:
thats right

[marcos713]

dont mean to thread jack but if your car does that is it a bad thing? mine does that as well but i never gave it any attention thinkin it was normal b/c the car was warming up

[Barefoot]

dont mean to thread jack but if your car does that is it a bad thing? mine does that as well but i never gave it any attention thinkin it was normal b/c the car was warming upif it goes away after the car get to normal operating temp your ok.

[tmracing83]

Good. But ima still look to fix mine. I'm under the hood now.

[Master Shake]

umm....why fix it if nothing is wrong?

a car idling higher on start up in normal for a lot of cars. it may do it just so it won't stall at first. and if the rpm's go back to normal....then...i mean.....whatever.

your car is fine. no need to start messing with anything.....

[Barefoot]

Good. But ima still look to fix mine. I'm under the hood now.
gl your going to try to fix nothing.

[tmracing83]

It bugs me. But thanks everyone

[Master Shake]

get over it man. its gonna happen.

[Master Shake]

tmracing83, you're a straight mother fucking poon ass bitch. sending me a PM calling me a dickhead cause i told your dumbass to get over some shit that you CAN"T fix? stupid ass

[tmracing83]

look how stupid u look....
i follow through with the first post
get to step 3 and tighten up a couple bolts and poof its fixed

"master shake" ur bout gay is it get bro. i enjoy ur entertainment... anything else to say that will make you feel any better?

i love how people can talk shit over the computer so easily... i live in conyers off exit 82 straight down 20
come and confront me if u want to be a fuckin man. plus ima little guy it should be easy to take me.
come and be a man now douche bag

ride out or fuckin grow up.

[Master Shake]

internet is serious business.

[Barefoot]

internet is serious business.lol u damn right it is. people get killed every day over the internet. the internet takes more lives than OJ.

[Master Shake]

lol u damn right it is. people get killed every day over the internet. the internet takes more lives than OJ.
:lmfao:

i just lol'd so hard.

[VickNotic]

if it aint broken, dont fix. That's how i'll put it 8D