Honda Prelude Revving Issue

[Doza]

Some of you may remember me from the old days--now, I lurk alot, but intend to start posting regularly again. Anyways, here's my issue: My car revs. When the accelerator is depressed, or I'm cruising, it does not, but when in neutral or stopped, it does. The revving is variable. When the engine is cold, it revs from about 1500 to 3000, when it is at running temperature, the rev ranges smaller, from 1000, to 1500. I've replaced the coolant temperature sensor, and no dice so far. Any suggestions or input would be greatly appreciated.

LintonDOZA

[johnnynumfiv]

What's your location, usually when the engine is cold, the rpm's are higher to warm the engine up, then when it gets warm, the rpm's go down. What do you mean by it doesn't rev when the accelerator is depressed?

[Doza]

It accelerates as normal. More or less, when I am sitting at an intersection, It will rev, when I am driving, It will not. It doesn't interfere with any operation i've noticed, but It's annoying and increases my consumption.

[johnnynumfiv]

What do you mean it will rev at the intersection? The rpms go up without touching the gas?

[Doza]

Pos. If the engine is in neutral(by not being in gear or being clutched) it revs in those ranges.

[DodgeNitroBIRM]

Have you tried pulling the throttle pedal up with your foot when it does that? And what year and engine is it?

[Quiggs]

Does the needle bounce a few times, or just once? If it does it repeatedly at idle, it might be a dirty or faulty throttle body. Try cleaning it. Run some fuel injector cleaner through your system.

My Golf was throwing a CEL and had a bouncy idle a while back, and it turned out to be a dirty throttle body causing it to stay partially open.

[Doza]

Reply it doesn't just bounce, although it has been a while since I've put any fuel system cleaner in it. The Car is a 1991 Honda Prelude Si with the 2049cc(2.1 is what it's listed as) engine.

[pimento]

I had an '85 BMW 323i that had a high idle when cold, I think it could just be that the engine is wearing out, so whatever mechanism is in place to make sure it doesn't stall over compenstates when it's cold.

[DodgeNitroBIRM]

I put more money on either a temperature sensor, the throttle body being dirty, or the throttle cable being gummed up. Check the cable first, then check the throttle body, etc.

[Doza]

Well, I'm pretty sure the issue is something electrical because when I take the Manifold Air Pressure(think that's the one) sensor off, It doesn't rev, but instead has a cold idle of 3k and a warm of 2k, along with showing the check engine light.

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If someone here is really slick with Hondas, I can get some pictures.

[Quiggs]

Have you tried asking on a Honda-specific forum, like www.honda-tech.com? They're going to know the specifics of your particular model/motor.

[Doza]

registered, posted, but no replies yet, they're just not as friendly as the folks here.

[preylude]

I had the same problem. It was the fast idle control valve. A lot of people say they never break, but they do apparently. Your best bet is to find one in a junkyard. We stole mine off of another engine they had in the shop.