Help me out here guys. Ventilation works fine except under hard throttle. IF I have vent or heater on and step on the gas then it switches to defrost vent until throttle load is reduced. No AC on this XL. Happens all the time.

Maybe related is a hard start condidion when there is high humidity. Only happened twice but I have to hold the gas down for 10 seconds after started to get it to idle or it will shut off.

Any thoughts?

 

This happened to my truck from time to time under hard throttle. Mine was under warranty and I took it in and made Ford replace some parts, I don't know which ones, and I haven't had any more trouble. Can you believe that they told me it was supposed to do that, when I first took it in for service?

 

I had a similar problem on an older model car. It turned out to be a vacum line leakage due to split rubber hose. Also, look for a vacum canister under the hood or dash which stores vacum under hard throttle. Anything with vacum lines going to the air distributor for the heater should be checked.