Idle high w/AC off and idle is fine w/AC on

We may earn a small commission from affiliate links and paid advertisements. Terms


New Member
Like the title says. When my A/C is on my 95 h22 accord 2 door idles fine, at about 500rpms. When I turn the A/C off, the car idles at almost 1.2k rpms. Can anyone give me a start on why this would happen? The IAC has been changed twice with no success. The VTEC valve was pretty clogged up last time I checked and was giving me idle issues (idle going up and down)- I cleaned it and the it fixed the idle moving up and down but the problem mentioned above still exists.

Check the fast idle valve or the as it too can be checked/cleaned

Were you idiling at 1.2K during the winter (when A/C was obviously not used)?

Is this a new swap? If could be an array of things that affect idle and such. It makes sense that your motor reacts to the A/C being turned on but not 700 rpm change.

Did you adjust idle because of the A/C (like turn it up to compensate for this drastic rpm change)?
The fast idle valve has been replaced and the issue didn't change. Over the winter the idle was fine, besides being erratic. There were no issues for a while but the high idle issue just started. Let me check the biss screw. I also need a vacuum diagram because I think I may have a vacuum leak. When I brake sometimes, there is a loss of pressure and I have to pump the pedal to tighten it up (or maybe just need to bleed the brakes)..
Brakes are seperate issue for sure.
IMO You need to get your idle in shape with A/C off
Adjust the idle

Allow car to properly warm up (Reach proper operating temp)
When fan kicks on thats when its ready

With motor running disconect IAC valve
Turn idle screw all the way to right CLOCKWISE
give it a rev see how it reacts
slowly turn to left COUNTER CLOCKWISE till idle smooths out
Check tach to see where the idles at

When your done adjusting turn vehicle off
remove the the radio fuse wait about 10sec.
plug IAC back in and check the idle.

If it works your good money
If not check the throtle cable for to much tension
also check to see if throtle needs to be cleaned.
As for the brake issue check for any vacuum leaks. This could be a cause of your high idle as well.
on my b16 the vac hose that runs from the IM to the brake power booster has a check valve in it, as well as a direction of flow marked on it. I dont know what happens if this check valve goes bad but it might be worth looking at.
I have the same problem:

93 Prelude SI (originally with h23) with Swapped JDM h22a full engine. Using m2s4 trans from h23.

New TPS calibrated
New IAC calibrated
Tested p14 (made for h23) ran perfectly. Tested p13 (made for h22a) which is made for that engine, stalled and died. P28 tuned for h22a runs but has issue original thread opener posted.

Engine stalls erratically during warm up when being accelerated. Turn A/C and other accessories and the engine does not compensate. The idle drops when accessories are turned on. No CEL lights.