95 Tahoe Idle Issue

[rmontgo21]

I have a 95 Tahoe with the 350 TBI and it seems to have an idle issue. The truck runs and drives great, engine is a jasper reman with 30k and runs like a top. The problem is idling in gear.

It seems that every ten seconds or so like clock work the idle drops 1-200rpm then rises up to about 900rpm. You can feel the truck lurch foward as the idle rises. It then idles fine for about ten seconds and does it again.

It almost feels as if something is clicking on like the AC compressor or something that briefly lugs the engine. Would this be the MAP or IAC sensor. I would think if it was a vacum leak it wouldnt be every ten seconds all the time.

Any info or tips would be great! Thanks!

 

[msteiny]

Do you have the windshield defroster on while this is happening? If you do the compressor will kick on and off to help pull moisture out of the air and defrost the windshield more efficiently. Also if you have had the A/C serviced recently and the engine is bogging that much, who ever serviced the A/C my have over serviced it and the result would be putting too much of a load in the engine. Try turning everything off and see if the engine still bogs down, if it doesnt you have just isolated the problem and might need to take it back to the A/C shop.

 

[rmontgo21]

Bingo! That was exactly it. I had the defroster on the last few days as it is getting chilly. The AC was serviced about 2 months ago and I threw on a junkyard compressor. Worked just good enough to get me through the summer.
Can I just unplug the connector on the compressor to disable it during the cold months? Seems excessive especially for an old truck to be constantly switching the compressor.

 

[msteiny]

Yes, thats what a lot of people do for the same reason.