I own a 1999 Ford F-150 4.2 litre motor V-6. Engine idles fine in drive but when I turn on the heater it idle

Question

s down then surges up. What's the problem? Thank you, Curt

Answer 1

hi, i have heard of this before, it boils down to be a character and very common of a ford, thats why you would see vacume hoses connected to a can of pork and beans painted black under the hood. ithink yours uses up all the vacume stored in that can of pork n beans and momentarily disrupt the idle speed diaphram. normal for a ford. but i would check for vacume leaks in the vacume hoses, make sure the brake booster is not leaky. check hissing sound near the brake pedal when not pressed. good luck

Answer 2

here's a artical on Ford engines that is interesting. (I found it on ebay motors guides)