engine dies when AC is on

[terry274]

My truck is a 1996 F150 with a 302 and automatic transmission, 133,000 miles. Plugs, wires, distributer cap and rotor are all new Motorcraft items. Ignition timing is set at 12 degrees advanced. (The problem was there before the timing was advanced) The fuel filter has been changed. The truck runs very well with one exception. If I start it with the AC on, it will normally die or run very rough. With the AC off it is fine. The problem seems worse when it is at operating temperature. Why is it doing this?

 

[NHGUY]

Maybe the AC compressor is starting to lock up....

 

[OVERKILL]

Could be the IAC (Idle Air Control) valve, as they were prone to blocking up with carbon on the 302.

 

[i_hate_autofraud]

Originally Posted By: OVERKILL

Could be the IAC (Idle Air Control) valve, as they were prone to blocking up with carbon on the 302.

Yeah, if the idle mixture is too lean, it can stumble and die with a load like that. See if it happens when put a little pressure on the gas peddle, once you open the throttle plate a bit, different air induction circuits overtake an IAC problem! Then the IAC is your 80% problem!

 

[dogememe]

iac valve very common try one from junkyard off wrecked truck preferably so you can be pretty sure it was working

 

[01rangerxl]

A/c compressor should probably have delayed engagement when starting, but I'm not sure on that truck. My 1994 Ranger delays the compressor until a couple seconds after it's started. Does your truck do this? If not, maybe look into that.

 

[FordBroncoVWJeta]

My 94 bronco did that when at a stop. Next thing I did I went down the highway and turned the AC full blast. Never did it again.

 

[Chris142]

Originally Posted By: 01rangerxl

A/c compressor should probably have delayed engagement when starting, but I'm not sure on that truck.

his does not have that. Turning on the ac powers the compressor up immediatly.

 

[Warstud]

Weak Alternator

 

[JTK]

So the stalling with the A/C turned on is only at idle RPM? Like said, possible IAC valve issue. I've seen A/C compressors lock up all at once and it will smoke the belt and can stall the engine.