I am trying to determine what is causing my truck to miss at idle. I just purchased a 1991 F250 with the 351. It has 108K miles and I do not know what kind of maintenance has been performed. I replaced the spark plugs and wires, cap and rotor, fuel filter, air filter. I also have a new PCV valve which I would like to install but could not find it and my Chilton's manual is in the mail, anyone have a pic of where it is located? I believe it misses slightly at idle and am wondering what other items might be causing this. Also, would I be able to take this truck to Autozone to get codes pulled or is it too old for this? Thanks in advance.

Brian

 

it could also be your IAC mine was worn and it felt like a slight miss.

 

In some vehicles, I think it is almost impossible to totally remove a small miss at idle.

Mine has a minute, almost undetectable miss at idle that goes away if I hold pedal at 800 rpm.
No codes, complete tuneup, new IAC. It remained even when I had engine replaced and used the original fuel induction (this is where the problem lies).

In some cases it may not total go away and will have to live with it.

It might be the TPS needs modification/adjusting to get within specs but the small miss at idle isn't worth all the effort to do so IMHO.

 

I think I am going to have the truck scanned for codes and also clean the IAC. The miss a little too noticable for my taste so hopefully I can fix it myself or bite the bullet and take it into a mechanic. Thanks for the suggestions.