I hope someone can answer this or has seen this problem previously. I've done a bit of reseach already, but have found very little that compares to or explains my problem.

I have a 96 Civic LX with original D16Y7 engine in it. Lately, the engine wants to idle at 2000 rpm. This happens after it's driven about 3-4 miles(not enough to fully warm up the engine, but well on it's way). I know the ECU tells the engine to run at high idle to warm up the engine, but 2K is a little too high, and it's never done it before so I know it's not normal. Now, if I shut the engine off, and restart it, it will idle at 1K or just a bit below just like it should.

Is this an Idle Air Control Valve issue, a sensor issue or something totally different? The car is an automatic and I don't like putting that much torque on the engine mounts by shifting in and out of park at 2000 rpm.

Any suggestions??

BTW, I have a pretty good knowledge of vehicles so feel free to go as far in depth as need be.

Thanks!!

 

sounds like either a sticking throttle or it could be advanced timing(unlikely) or could be the carpet holding the pedal down.

its its a sticking throttle you just need to clean the throttle body butterfly plate could be a bunch of crap causing it to be stuck open.

 

have you tried resetting the ecu lately? That might solve it....

automatic '96 lx's should idle around 700rpm's or so. Thats where mine sits at.

 

750 RPMs

 

That would be a very logical place to start. I'll try doing that. Do I need to run the car for a certain amount of time after resetting the computer? I've heard 15-30 min after it reaches operating temp so that the computer relearns sensor information.

I did put a can of Sea-Foam in it tonight thinking that may help a bit should the IAC valve be dirty and sticking.

As far as a sticking throttle...
If I shut off the car when it's doing this and restart it, wouldn't the idle remain at the higher RPM? That's what confuses me, because if I shut it off and cycle power to the ECM, it seems to correct itself. That's why I think that Will might be on to something.

Thanks everyone for their input!!

Any other ideas are also appreciated!!

 

Did you use the SeaFoam before? At a shop that I managed, we had some trouble with SeaFoam... running it through the vacuum system. It was causing high idle/ or stalling problems, because of the SeaFoam deteriorating the vacuum hoses and clogging them.

Check the vacuum system, even if you didn't use it before.

And I also agree with NeverBX :cheers: ...sticking throttle, among other preliminary checks.

 

if its the IACV it wouldnt stick in one place it would constantly fluctuate 1000-2000-1000-2000 like as if soone was reving on you.

if its really cold where you are it could be the timing since the ecu advances the timing every 11 degrees when the rolling intake temp drops.

if its your timing heres a test when the car is idling just tap the gas about 1/8 if it drops back down to 700-1000 then its your timing cause of the cold weather.

 

vaccum issue.

 

yup thats what it sounds like to me

 

This is the first time I've tried Sea-Foam. I normally use STP every third tank of fuel, but I thought I would try Sea-Foam as I've heard it's a bit more potent then STP F-I cleaner. I didn't run it through the vacuum system though as it recommends on the can, I just put it in the tank with fresh fuel.

Where might I check for vacuum leaks? Are there hoses that are prone to failure that you could point me to? I've never had the manifold off and the bolts appear to be tight, so I'm assuming the gaskets are still intact. Is this a good assumption to make? The car has 130K on the clock and still has all original vacuum hoses on it, so it probably wouldn't hurt to replace them just for safe measure.

I will also check for a sticking throttle, as that seems to be a widely acknowledged idea.

Thanks to all!!

Thank you for explaining how the IACV works. I am very familiar with the GM IACV but didn't know how similar/different it is to Honda.
The temperature has been a bit cold here lately, but not that cold. It's been between 20 and 30 degrees F when my problem has occurred.
I have tried bumping the throttle a bit but to no avail, the only way to decrease the idle to normal, is like I said, turn off the engine and restart it.

Thank you again for taking the time to explain the IACV and timing to me!!