92 S10 Chevy Blazer 4.3 CPI High idle when engine is at operating temperature only.

Mine idles quite high at operating temperature. After its been parked for a while it idles OK. Idles OK when 1st started, most times once it reaches operating temp, about 195, it has the high idle.

Tried to check for vacuum leaks with a butane torch and spraying carburetor cleaner on vacuum lines and intake areas. Can it have a vacuum leak only at operating temperature? For it idles perfectly until its warms up.

I have tried to check connectors at IAV, MAP, TPS, CTS, as well as at the computer, all seems well, replace IAV & TPS. The old TPS when going from idle to Wide Open throttle it would only reach to 3.28 Volts, yet the new one does the same.

Before replacing the TPS I was getting a code 45, since them I've driven over 100 hundred miles without no codes. Plus I have notice since replacing the TPS it no longer surges when you let off the accelerator to slow down, before replacing the TPS surging was very noticeable anytime you let off to slow down.

I've pulled the MAP and the EGR off just to look them over, all seems well, the EGR was replace a couple of years back becasue it was giving me troubles and it looked A OK.

Disconnecting the IAC valve will usually bring it back to idle, while its disconnected the service engine light will soon come on and it will throw a IAC code.

 

Today I found one problem, why my throttle position sensor was not going to full voltage, my throttle is hanging. Have not figured out just what is causing this. After finding it was hanging I tried it several times, probably once out of every five times it hangs at about 3.38 Volts, when it opened fully it goes to nearly 5 volts. At least I now know what the proms is with that.

And I thought I might have found my problem with high idle, I pulled the PCV line off along with the 2 short pieces of rubber line, when I would put my finger over one end, them blow in the other end, it was not holding full pressure. Yet when I replaced those to small pieces of rubber line that did not cure the high idle.

From what I understand a vacuum leak is the main thing that will cause a high idle.

I suppose that not getting no replies means no one has any suggestions. Searching the net I came across several post with others that have this problem, few of them seem to find the answer and or they never post back the answer if they did cure the problem.

 

This may sound over-simple, but did you clean your throttle body when you replaced your TPS? A dirty throttle body can cause your throttle to ''hang" .

 

Mine is a CPI not a throttle body, yet the intake is very clean inside. Haven't figured out why the throttle hangs at about 3/4 throttle.

I feel that I ruled out a vacuum leak. I took off the vacuum line from the back of the CPI body, hooked up a vacuum gage, still high idle.

I took the brake boost hose off at the engine, plugged it off, no change, and I have already made sure that is not a leak in the PCV valve or its hose.

And I've already gone around the intake with a unlit butane torch with it turned on, it had no effect.

We've got bad weather coming at us, its dropped from the 40's early morning to the 20's. After this passes through I think I'm going to have to take it to my friend that has a full computer he can hook up to it, I've run out of ideas.

Thanks for the reply. Would have answered sooner you sooner, but Sunday evening when I returned from church we had a rain, thunder, & lighting storm, it got my PC, Now I'm having to use my old one till mine gets repaired.

I made one mistake, I had everything backed up to an extra hard drive and to disk, except for my passwords.