89 4x4, 4.9 inline 6 dies when the AC is turned on

Southfork894x4 · #1 (**permalink**) 06-17-2012, 07:53 AM

Just bought my first ford 4x4, truck runs great until you turn on the AC. Motor will stumble with RPM's going up and down until it just quits running. Turn off the AC and it cranks right back up and runs fine. The idle control valve has been replaced or at least the guy said it had been when I bought the truck. Just not sure how to start trouble shooting this issue. Any help would be a big plus. Thanks Guys

Eddiec1564 · #2 (**permalink**) 06-17-2012, 08:09 AM

What happens if you throttle it up? Does it still lug the engine down or runs? Also does the AC work when driving down the road? Could be a AC compressor locking up or the ECU is not seeing the AC on command to idle up the engine (pin 10 on ECU goes to AC clutch).

My 89 F250 does the same as I have a bad connection from the AC clutch to the ECU pin 10. It will surge the idle at start up and sometimes stall if I have the AC on.

Southfork894x4 · #3 (**permalink**) 06-17-2012, 08:18 AM

If I give it gas it runs fine but as soon as it idles down the engine dies. I will check the connector as well and see if the AC clutch is kicking in.

Eddiec1564 · #4 (**permalink**) 06-17-2012, 08:54 AM

If the AC is working while driving down the road. I recheck the idle air valve. The passage ways could be plugged up going to it even with a new one.

Southfork894x4 · #5 (**permalink**) 06-22-2012, 09:45 AM

Checked the ICV and did not see and plugged port holes, cleaned it out anyway and then back on the truck. Same issue as before but I have noticed that at times the idle will drop way down and act like it is going to die and then rev back up. Does this a couple times and then idles right for awhile. Most time it does this when down shifting to stop or turn. It also will shut off sometimes as well. TPS, ICV, Air leak not sure which way to go.