98 F-150 XLT, 4.6, misses when the A/C switch is put in the A/C or Def positions. Within minutes of turning on the A/C compressor, the truck starts to miss & the check engine light flashes. After a few minutes of driving with the switch off, the truck starts to run better, and after a couple of hundred miles, the "Check Engine" light goes out. I have changed all spark plugs, both coil packs, and plug wires. Please Help!!! I just found out about this web site from a Ford dealer's service writer today. He suggested asking here before spending $$$ for service.
Truck has 200,000 miles on it. If not missing, is STRONG! Used Mobil 1 oil from start, has towing kit, but never towed anything. The in cab thermostat doesn't work, you can turn the dial from cold to heat, but nothing happens. The intermittent wipers do not work. But other than that and this A/C related problem the trucks runs good. Just had all of the front ball joints changed, and would like to keep the truck. Need help.

 

Might try taking it to the local auto parts chain. They sometimes pull trouble codes for free. If you post back with the codes someone here may be better able to point you in the right direction.

 

I'll try to get the code from the computer tomorrow. Thanks, BTW, I will also try to move the wiring harness near the A/C tank that I read about in another post.
Thanks to all of you. This site is great.

 

I repositioned 2 wire bundles that were touching the air conditioner accumulator (passenger side near the firewall) this morning, and I drove with the air conditioner on for about 50 miles today. No miss, and the check engine light went out. Sure is nice to be able to turn on the defroster on a rainy day again.