Idle too high on hot starts

[teleplayer]

I have just finished plugging up every vacuum leak I could find, including a bad s/c gasket, leaky vacuum tank, leaky s/c solenoid and cannister purge valve. The car idles and runs great now but I still have this nagging hot start problem. If I shut off the engine when it is hot, and then re-start ~5 minutes later, the idle starts off at about 2,000 rpm and slowly makes its way back to normal. Does not happen every time. This wouldn't be such a big deal but my trannie has that sprag or overrunning clutch problem where it catches and bangs at high idle, in park.

I thought maybe I had a bad engine coolant temp sensor, but it's reading ok on my scan tool, both cold and hot. I was wondering if it could be a leaky injector, but all the posts I have seen mention that this causes a hard start.

Throttle body is clean, IAC is clean, but original.

Any ideas?

[bad.moshi]

I used to have high idles at startup regardless of the temp. It turned out to be my TPS. It eventually threw me a code but I was having issues for a couple weeks before it did. Try unplugging it and starting up hot just to see how it acts.

EDIT: This most likely will throw you a SES because of the broken circuit, but it's worth a shot to see if that's what's causing your problem.

[Cheetah]

I would start her up in netural with the parking brake on of foot on the brake until you figure out what it is.

What is the initial idle when it's cold?

[teleplayer]

Thanks for the TPS idea. I will have to keep my scan tool plugged in and see what the TPS reading is before I start up.

It bangs in neutral too. I have tried slipping it into drive, but that isn't much gentler ! I suppose at least it wouldn't be hitting the parking pawl, in neutral.

I normally see it go up as high as 1500 rpm when cold, or when slightly warm. That doesn't seem to be a problem. It's when it zooms up to 2000 or so, that is bad. Does anyone know what determines the idle speed commanded by the PCM?

[Cheetah]

No code means the pcm is seeing everything as "normal".

Check the vaccum line going to the brake booster and the check valve. If you don't know what that is, let us know. I had to replace mine on my 97 Ei. Hitting 1500 rpms when cold is not good either and will only get worse as it gets colder outside and when the PCM commands more air and fuel

Have you done anything to the TPS recently? As a side note, have you serviced the trans lately?

**Edit** I'm guessing there is a slew of things that control the idle - coolant temp, outside air temp, a/c on or off, ect...

Also check the plunger on the IAC. Those can go bad. The fact it's intermitent may be a sign that it's failing.

[bad.moshi]

yeah it seems lots of things control the idle speed. i was told to look at my PCV valve as well to make sure I didn't need a new one. I eventually got a code saying it was a high-voltage signal coming from the TPS, but it took a few weeks for that to show up. It only occurred occasionally at first, but then everytime I'd start up it'd shoot the RPMs to 1500+, sometimes slowly climbing above 2500. Needless to say I would start and shift into gear before it'd start it's climb to avoid the trans thunk.

After unplugging the TPS, it started just fine. I plugged it back in -- high revs. Unplugged again, just fine. So that was my problem.