91 C1500 Almost kills then fine

[oldchevy]

I've had this problem with my 91 c1500 4.3L (170,000m). After I start it, it idles fine and then when i shift it into reverse or drive, it almost kills..drops as though gas was shut off, it doesn't kill, but damn near. It seems to find or adjust it self very quickly and then everything is fine. No other idle issues..maybe a little rough every now an again but nothing noticeble.

Any ideas?

New:
temp sensor, fule pump (3yr), failsafer therm, caps, etc, just about everything else..

[horse482]

Could be the idle air control valve is getting gummed up and needs cleaned or replaced.

[alblogg]

Originally Posted by oldchevy

I've had this problem with my 91 c1500 4.3L (170,000m). After I start it, it idles fine and then when i shift it into reverse or drive, it almost kills..drops as though gas was shut off, it doesn't kill, but damn near. It seems to find or adjust it self very quickly and then everything is fine. No other idle issues..maybe a little rough every now an again but nothing noticeble.

Any ideas?

New:
temp sensor, fule pump (3yr), failsafer therm, caps, etc, just about everything else..

Has the battery been unhooked or changed before this started?

[oldchevy]

thanks for the feedback guys.

The IAC is about a year old..i could try to clean it. I have not cleaned it.

The battery is constantly connected and reconnected due to working on other part of the truck etc. What is the connection between the battery being connnected and reconnected and a momentary idle slump. It does this slump thing every day on first start, not just the time after I connected the neg. lead. Please advise.

thanks

[alblogg]

Originally Posted by oldchevy

thanks for the feedback guys.

The IAC is about a year old..i could try to clean it. I have not cleaned it.

The battery is constantly connected and reconnected due to working on other part of the truck etc. What is the connection between the battery being connnected and reconnected and a momentary idle slump. It does this slump thing every day on first start, not just the time after I connected the neg. lead. Please advise.

thanks

Sometimes if the battery has been unhooked for what ever you have to sort of retrain the truck to idle correctly. You can try cleaning your IAC but if it don't work start your truck put it in rev be sure to have the E brake on and let it sit and idle for about four to five minutes. Oh by the way don't leave your truck unattended unless you really trust your E brakes. This will reset the idle if that is the problem.

[oldchevy]

thanks for the input guys, but none of this has helped. Strange problem. Now that's it got up to 100 degrees again it's not as bad. When its been cold, it acts up again. It has to have something to do with the temperature, but like i said, i just put in a new sensor..

any other suggestions from anyone?

thanks all.

[profox02]

will i had a problem like this in my '91 350...like you i checked everything i could and nothing...then someone said to check the rotor...not the cap and just the little thing dat spins on top..but the rotor shaft...i pulled mine and oil a few spots dat looked like it needed it...and no more problem, runs good and no more stalling in the drive way....but i would suggest replacing it if it looks bad to you..