IAC and TPS - 1994 Delta 88LSS

First, hello to all. Seems like a great website for car help. I'm an American living in Moscow, Russia, which presents a heck of a problem with getting parts. That being said...

Here's my comment and question(s): I've been having problems with what I thought was my IAC. The car has 185K on it, and recently died once or twice while going about 30mph when I let my foot off the gas. Restarted in neutral. Then it began starting cold at about 1600-1800rpm, but I shut it down immediately.

Unhooking the IAC and blocking the intake hole before starting resulted in a starting rpm of about 1K, but with fluctuating. I replaced the IAC. Still started at 1800rpm or at 2200rpm; it's random choice.

At my wit's end, I figured on leaving the IAC in and just unhooking it and then starting to see what it did. After starting cold, it idled perfectly at the correct choke setting, then gradually dropped as the engine idled and warmed, until it was at perfect idle. When I was getting ready to drop the hood and go for a spin in my neighborhood, I noticed I had mistakenly unhooked the TPS, not the IAC. What the heck? I thought the TPS had nothing to do with idle speeds???

Anyway, I drove it, goosed it several times with no apparent problems, but because of the speed limit here, never went above 20mph. No problems at all, except for the check engine light of course (the TPS was still unhooked). The car is a hybrid, meaning it has the OBD1 computer with the 16-pin OBDII plug. (:screwy:) I just replaced the ECM with a used one and well, everything seems to run fine without the TPS hooked up, with the exception that I take a MAJOR chance if I take it out of our compound and can't get it back because it stops running (towing would run in the hundreds of dollars).

Sorry about this taking so long, but do any experts on here have an explanation as to whether or not my high-idle problems disappear with the TPS unhooked? Thanks and regards, Steve.

EDIT> I put Raytown, MO on my profile as that is where I once lived before transferring overseas

The tps could be bad, go to autozone.com, repair guides for the checking procedure not using a scanner, using a DVOM instead.

The tps could be bad, go to autozone.com, repair guides for the checking procedure not using a scanner, using a DVOM instead.

Thanks for the reply. Unfortunately, there are no autozone stores in Moscow. As mentioned, me and the car are in Russia, and I haven't seen another Delta 88 in my two years here.

About an hour ago I started the car, which again idled perfectly. I went to plug the TPS back in and the engine started racing immediately. Of course I unplugged it, which returned the idle to normal. Strange.

Thanks, S.

I think I may have found the problem by accident. I'm posting this in case it helps somebody else.

While I did do some research on the IAC, cam sensor, crank sensor, O2, TPS, etc; the other day I decided to unhook the IAC and start the car to see what it does. Well, it started perfectly, at the correct rpms, idled smooth, and when warmed up, the idle dropped to the correct rpm. So I jump out to see what happens when I reconnect the IAC and notice that I had accidently unhooked the TPS instead. :slap:

So I go to plug it back in and the engine immediately starts racing again. I pull it back off and the engine idles back to normal.

WTF? I thought the TPS had nothing to do with idle, but operated only under load?

In any event, I have a new TPS coming in the mail. Looks like it might do the trick.

BTW, I said autozone.com a website, not the store. The tps tells the pcm when the engine is at 0 throttle so the isc can hold the idle speed.

BTW, I said autozone.com a website, not the store. The tps tells the pcm when the engine is at 0 throttle so the isc can hold the idle speed.

I'm always a stickler for details, and yet I missed the dot.com at the end of autozone in your email. Sorry about that.

But, all's well that ends well (almost). Thanks for your assistance. I've seen you all over the website helping others. Absolutely invaluable.:thumbsup:

Best regards