idle

[tinman]

I have a 96 s-10 4.3 V6 and whenever i have the heat on and sitting at idle it revs up to about 1000rpm then back down and does it about every 5-10secs but doesnt do it when the heat or def or anything is on, also do notice is slighty when iam driving at low speeds and rpm just like a lil surge. Does anyone have any ideas of what could be the cause of this thanks for any help u might be able to give me.

[tinman]

anybody?????? help please

[Old Man]

Cant doesnt make any sense. Does it with the heat on and in the next sentence doesnt when the heat is on.

Ass/u/ming the rest. Well when the defrost is on and also sometimes when the heat is on the ECM commands the AC to engage. During defrost cycles the AC is used to reduce moisture within the air so it doesnt fog the window and helps remove frost. During heat cycles it also can come on to one maintain temp, 2nd to also again remove moisture while maintaining the clutch activation of the AC.

Its normal!

[tinman]

"doesnt do it when the heat or def or anything is on"

when the heat is on it acts up when its not on it is fine i typed it correctly the first time

[Old Man]

""""""I have a 96 s-10 4.3 V6 and whenever i have the"""""" heat on""""""" and sitting at idle it revs up to about 1000rpm then back down and does it about every 5-10secs """""""""but doesnt do it when the heat or def or anything is on"""""""


Counterdiction!!!! Both times the term HEAT ON is used!!


Again, what I ASS/U/MED is the response. When the ECM commands the AC on, the idle speed will increase until its fully engage then the ECM commands the normal idle speed. Same goes while cruising, when the AC engages, and it is a brief period of time, does the same thing! Its not staying on, its cycling on and off and is normal!

[tinman]

sorry my bad. ok thank you, so it doesnt have anything to do with the EGR valve?

[Old Man]

If the EGR valve stays even semi open a idle, it'll either completely stall out or have a very hard time holding idle. It wont bother upper rpms areas since this is when its suppose to be open..

Ok, The AC works like this and you'll find this in the owners manual in some form.

Selector off- AC wont cycle
Selector on feet, dash mixed- Only will cycle when heat is set below half way. Will sometimes cycle during only cruise to keep the clutch free.
Mixed Defrost and Feet- It'll cycle on and off just like you posted.
Defrost- Also cycles on and off, but with more draw!

All you have to do to see it in operation. Have someone in the cab, you open the hood and watch the AC compressor. You'll see the belt go round, but the main center of the AC isnt moving. Have them set it to either defrost cycle and you'll see what it does. Compare that to what your seeing in the cab driving, I bet its the same!