Idle up and down

[slvarner]

I have a 99.5 7.3 all stock engine and It use to idle up and down on warm up. I have noticed lately it does not do it anymore. What should I look for. Thanks for any help.

[ford crazy]

usaly in warn weather one its up to temp i wont do that . now in cooler weather it will go up and down to keep its temp up . if the thermostat has never been changed change it and does your temp guage work. look to see if its low norn or running hotter than normal

[ford crazy]

O i for got look and check out your exhaust back pressure valve it may be bad or the tube going to it may be obstructed and needs to be cleaned out.

[no-tel-in]

In Cold weather (teens-20's) mine will idle up. Has never done it other than those really cold days, and typically in alabama huntin