So I finally managed to get my 81 F100 (inline 6 - Carter YFA Carb) running more smoothly but now that's it's back and working it reminded me of a problem it has. Simply, it idles higher in park and neutral. Is this a vacuum issue. Is this an IAC issue? Does this truck even use an IAC? Thanks in advance.

 

That's true for any engine because there is no load on the engine out of gear. It's normal. How much higher are we talking?

 

I can understand the logic of that but I'm not sure that's true. I have two other cars that I have paid attention to while changing from one gear to another. There was no difference. They are both fuel injected though...not sure if it's any different for vehicles with carburetors.

The difference is noticeable. It has a very steady idle while in drive and then a noticeable increase in park...not enough to cause it to diesel or anything though.

 

bound to be a difference between carb and injection far as idle . Though shouldnt be more than couple hundred rpms in gear or out of