93 accord erattic idle

08-24-2011, 01:21 PM
i recently noticed my 93 accord idling between 1,000 and 2,000 going up then down up and down when the car is in park but when i shift it into gear the car idle goes down to 700 but after driving i shift the car back into park the idle goes back up 1,800 rpm levels off than comes down to 1,000 rpm and i know this idle is too high because it cause my fans to come on sooner and more frequent its like im on the gas when im not i did some research and came back fitv fast idle thermo valve so i changed this valve twice and it still does the same thing i have no coolant leaks and no intake work was done so i dont think its a vacuum leak cause it only does erattic idle in park but in gear its fine so this is a puzzling one also i changed thermostat and flushed cooling system followed by a bleed of all the air out of the cooling system now on youtube they call this a hunting idle and is very notorious on 90-93 accords also when i drive down the road and let off the gas it lets of this high pitched whining noise sounds like a valve is getting stuck open or as my daughter calls it an elephant so greenblur if your out there this is your curveball or anyone else that has had this problem and fixed it

08-24-2011, 02:37 PM
I dunno...my first reaction with a hunting idle that rolls up and down over a wide range on a Honda is always to VISUALLY VERIFY coolant level IN THE RADIATOR, with engine warmed up and running...what you see in the reservoir is meaningless, if it's leaking anyplace. Sometimes they won't siphon properly if so. They roll up and down because the coolant is surging back and forth over the temp sensors and thermostatically controlled fast idle speed valve, sending the PCM into a tizzy trying to keep up.

But if you have some kind of wheezing sound when drop the throttle, this is when manifold vacuum level is highest, you are hearing disconnected vacuum source or a failing vacuum diaphragm in a control assembly....now I gotta think what could be the relationship...dammit...I hate thinking... :)

See what I can come up with...

08-24-2011, 03:34 PM
I know it is the first time I have ever heard of this first thing I thought was a valve because it sounds like a valve that controls airflow is getting stuck open and when vacuum lowers it closes but it just puzzles me and I have had this car for 13 years not one problem other than your regular maintenance and broken motor mounts and such also no check engine light either

09-18-2011, 01:32 AM
My 91 Accord had the same idle issue. I did alot of research on here and other places. Anyway, I replaced the IAC Valve (Idle Air Control) and solved the problem. Hope this helps you.

09-18-2011, 02:25 AM
I'd be looking for a vacuum leak somewhere.

They will cause an erratic idle (surging) and maybe the source of the high pitch noise

09-20-2011, 10:27 AM
update replaced fitv and even after the car is fully warm when in drive it doesnt surge but as soon as i put it in park it goes from 1000 to 1500 and bounces back and forth but as soon as i unplug my idle air control motor the idle surge stops and idles normal and im not sure its vacuum related because both these valves are controlled by coolant and as soon as i unplug the iacm the problem stops errggh

09-20-2011, 05:20 PM
My 91 Accord had the same idle issue. I did alot of research on here and other places. Anyway, I replaced the IAC Valve (Idle Air Control) and solved the problem. Hope this helps you.

Ok after extensive research I keep hitting a wall saying my idle air control valve is bad because everytime i put the car in park it will fluctuate between 1000 and 1500 rpms I have to hit the gas for it to level off and come back down even then it will only idle at 1000 rpms but in drive it idles perfectly fine but soon as i put in park it idles up and down up and down and there is no coolant leaks and bled coolant system several times via thermostat housing bolt so my next question that no one seems to have the answer for is how do you test your iacv is there like a procedure I mean I unplug the iacv when the idle is going up and down and as soon as i unplug the iacv it stops going up and down so I would assume that's the problem hey greenblur I know you are out there this one is right up your alley

10-13-2011, 11:56 AM
I was facing the loping idle issue in my 1992 LX. I knew about the FITV (fast idle thermal valve) which is to the right of the IAC (mounted to the intake). take off the 2 screws on the top and you can use a flat blade screwdriver and turn the white plastic piece down until it stops, then back it off about an 1/8 turn. This would stop the surging.

HOWEVER, I totally took mine apart, and cleaned it. used a little honda bond sealant on the o-rings as they were pretty flat from being in the car forever. The o-rings are cheap at the dealer, but I really did not have a way to get to the dealer, as it was already out!..... anyway. the loping stopped....or so I thought!

***I should mention the other issue my car had is it would idle at 1500 rpms, which is way too high. It would also rev from about 1100 - 1500, not all the time, but sometimes...???? (not sure why).

so I followed the process in the service manual on how to reset the idle, well my idle screw was far enough out that it was leaking air by it! I adjusted the idle to a normal level (about 800 rpms) and my loping is now gone as well.

with your car running, unplug the IAC, the idle should drop right away, if not then the IAC is not working, or a wire is bad, could even be ecu, but most likely the valve itself.

IF it drops, and your idle is higher than it should be, you may want to try adjusting the idle.

process is car fully warmed up, and engine off unplug the IAC, next start the car, ... you may need to push on the gas pedal a little to keep it running, and it will eventually maintain an idle. The idle SHOULD be about 100 rpms lower than the idle your car should be at. typically about 600-700 rpm is OK. If it is not at the level, then you need to adjust the idle screw on the throttle body, it is right below the red hose, and right above the intake hose (the one that goes to the air filter box). turn it clockwise to lower the idle, or counter clockwise to raise idle.

once you are happy with the idle, turn car off, plug in IAC and pull the 7.5 amp "backup" fuse in the under hood fuse box for 10 seconds... put fuse back in and start the car. the idle should now be roughly 750 +/- 50 rpms (at least on a manual transmission that is correct). next is to turn on lights, heater fan, rear window defog, and it should maintain the 750 idle.

OK so either I helped you, maybe someone else, or typed all that for nothing! It worked for me though. I was about ready to order a new FITV, now I don;t need to!

10-14-2011, 10:57 AM
This is a pretty good fix!


I believe Eric The Car Guy has a video on this topic on You Tube. If I find it will post it here.


11-26-2011, 11:56 PM
Update erratic idle solved turns out my idle screw on the throttle body was adjusted too rich aka high idle I learned a process in order to set the computer right you need to disconnect iacm idle air control motor of course its gonna trigger a dtc check engine light code 14 for iacm but once you have disconnected it than set your curb idle of course use a digital tach anywhere from 600-700 +/- 50 rpms then remove battery backup fuse for radio also holds computer codes so remove fuse for 10 seconds than plug iacm Bal in than plug in fuse and start car my adjustment took a few tries but now my dreaded Honda idle is gone and I'm good to go any trouble let me know I will let you know if I tried that or what to try and do thanks for all the support

11-28-2011, 08:09 AM
also i forgot to add when finished you need to put some silicone on the idle screw so it doesnt back out no dont use jb weld or any liquid steel product because this screw has to be serviceable for future use and or adjustments and cleaning

06-22-2015, 03:00 PM
way to go, Jaybur_racing, i followed your post and it worked great i have a 1992 Honda accord ex that was surging from a 1000 to 1500 on RPMS. but not anymore. thanks again.

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