My truck is idling funny when it has sit overnight and i crank it up in the mornings. It will go up to 2000 rpm's then come down to 1000 rpm's then eventually shut off. After i crank it back up it goes back to 1000 rpm's and settles. Usually it runs pretty good after that. I cleaned the throttle body and put a new idle air control valve on but still the same problem.

 

for starters:

how black is the tailpipe?

Do you have a way to get any PCM codes read?

is the check oil light on or does it even work? check engine also?

 

No check oil light is on. The tailpipe is pretty black on the inside. Sometimes i can smell gas pretty strong.

 

My doctor said, "Don't let it sit overnight"

I didn't get it.

 

On the upper intake plenum, left center, you will see a round canister with a wire sticking out of it, bolted into the manifold. This your idle air control valve or IAC. They often get gummed up and cause poor idle. Take it off, and really soak it down with your favorite parts/carb/brake cleaner. That can cause an erratic idle like you describe.

EDIT: Just saw you already tried that, disregard above.

How does it eventually shut off? RPMs gradually drop lower and lower until it dies, sputters to a halt, or just cuts straight out?

 

Usually the rpms get lower and lower until is stops. It is pretty gradual. I usually just cut it off and turn it back on. That usually works to get the idle back up to around 1000. This morning it went down to around 500 rpm's and tried to catch back up before shutting off.

 

I have a similar problem on my 88 2.3l. Mine does the same thing on a cold start, but usually doesn't stall. It does seem to idle fast after warmed up. About 1400-1500rpm.

I am going to try and clean the IAC. Sounds like a good start. Also just bought it so probably need to check all the tune-up items.

Allen