Idles bad when I turn the Fan on

[Rangerfan2.9]

Today when i was starting my truck i noticed it was ideling really bad. It almost felt like it was gonna stall out but didnt when I turned the defrost off.I have noticed it did this maybe a couple times but i didnt realize that turning the fan on and off made a difference. After it warmed up I also noticed that when I switched the fan on my Idle was slightly worse than with it off. Not by much though, the rpms were slightly bouncing around compared to it being perfect with it off.

Could this be a timing problem? I

I noticed the top pully which i think has to do with the fan that has a plate that spins clicks on and off alot when the fan is on. My gas mileage has been horrible since the day i got this truck.

[jswag5]

thats ur a/c pump, it will run periodicly when ur defroster is on, and it will bog down ur motor. but i highly doubt its a timing issue. get urself a tune up, whole nine yards, plugs wires filters and fluids then check back, that right there should cure ur prob.

[Rangerfan2.9]

already did all that I made a thread about it. But i wouldnt think it would cause it to bog down to the point is was almost ognna die

[jswag5]

i know when running a/c in my 95 blazer it really bogs down, and did you check for a faulty coil cause ive had a faulty coil cause a slow idle issue, and you may also just have an exhaust that isnt exhausting proper, check ur catalytic converter and o2 sensors.

[Rangerfan2.9]

i know when running a/c in my 95 blazer it really bogs down, and did you check for a faulty coil cause ive had a faulty coil cause a slow idle issue, and you may also just have an exhaust that isnt exhausting proper, check ur catalytic converter and o2 sensors.

Yeah but im not turning the AC on im just either running defrost or the vent. No i havent checked the coils, I thought that would casue a different idle symptom? Ive had a bad coil in my ranger and it would cause the rpms to jump up really high.

Also has a new o2 sensor, gutted cat, and muffler seems fine.

[nomaboy]

on the 4.3 trucks when you have the defroster on, the computer will kick the a/c on and off as needed. so by running the truck in defrost mode you are useing A/C. if anything it is the computer not bumping the RPM's up when it kicks the a/c on like it is soposed to or the IAC(idle air control) is not working right

[Rangerfan2.9]

would the IAC become more symptomatic with the air on? It was sputtering hard like it wasnt getting gas, but boom as soon as the air was turned off it was fine. And when it warmed up it wouldnt do it.

[nomaboy]

the iac controls the amount of air allowed to pass through the throttle body when the engine is at idle. when the a/c gets turned on, the computer is soposed to tell the iac to open up a bit so the idle rpm will raise. the a/c puts a load on the engine and in turn tries to slow the rpm down. so to fight that the iac allows more air to pass into the engine and raise the rpms a bit to keep the engine running smooth. the problem you are having is hard to diagnose to a cirtain part with out looking at it.

[Guidare]

Unplug the AC wire from the pump, your defrost will still work. If that stops the problem you can narrow it down. I unplug mine in the winter for MPG, but you should run it at least once a month to keep the AC seals from drying out and leaking.

[nomaboy]

Unplug the AC wire from the pump, your defrost will still work. If that stops the problem you can narrow it down. I unplug mine in the winter for MPG, but you should run it at least once a month to keep the AC seals from drying out and leaking.

same here

[Tink]

With my 00' BlaZeR2, it idles bad with the fan on... you can definitely see the rpms bouncing around. Turn it off and it idles fine. I also can even feel a surging going down the road with my truck... I think my problem is the alternator... the voltage is a bit low compared to all my other gms, so I think the alternator is starting to go and can't quite keep up with the voltage draw when the fan or AC or defrost is on... so it is dropping the voltage which drops the voltage to the sensors, causing the rough idle and surging. Turn the fan off, it can keep up with demand and rough idle/surging goes away. SO, what is your voltage gauge reading w/ and w/o the fan/AC/defrost on?

[Mikz86TA]

Most likely its a bad or dirty IAC motor/passage. The alt. would cause more than idle problems. Every electronic device has a min and max operating voltage. If you are below the max they work slowly,poorly or not at all. If the coil was starved for power it would need to drop below 11.8V DC . At that voltage your headlights would be very dim, the blower fan would not work on high as it normaly would spin at that setting and other higher current would fail.