during cold weather (Zero area or below) my '99 F-350, 7.3 has a slight but noticeable rpm surge at low speed. Usually approx. 50-75rpm change. I can hear it and looking at the tach it bumps up ever so slightly. After low (slower speed 5-20mph) speeds it is fine and if I drive it a bit and stop and restart it is gone??? Hmmm? what do I need to check or replace? thanks, new member but love the forum.

 

I just asked a similar question and posted a video of what was happening.

https://www.ford-trucks.com/forums/1...l#post14107088

Consensus is it's normal.

 

It's suppose to do that. Its fine after you drive it a bit because the engine has had a chance to warm up. Generally, it will do that as soon as you start the truck and once you put it in gear the idle drops but then it will run at higher idle until it warms up....no worries.

 

Stinky makes a bizarre noise at about 100 degrees F Engine Oil Temp (first line on dash temp gauge). The engine is in transition from one running mode to the next at this temp, and it's barely noticeable unless you're listening close. I know to expect it, and just roll with it. There are many things these trucks do under specific circumstances that raise an eyebrow when you first discover them... but the truck's been doing it all along, and somehow we survive and keep racking up the miles/years.

 

thanks for the information. I understand the "fast idle" warm up but this happens WHILE driving. Always (in cold weather) at a slow speed. It is like you press and let up on the gas pedal ever so slightly.... that is what it is like but I am certain it is not the pressure by my foot on the pedal.