Good evening. I have a 97 F150 4.6 4X4 with around 178,000 miles on it. The truck has an issue where it will idle extremely rough and then continue this "rough" style while I drive. It is not an everyday occurrence. Sometimes it happens and sometimes it does not. The truck has new
plugs and wires
Mass airflow sensor
had a compression test about 4 months ago because of the same issue (everything appeared fine and no leaks)
did an intake cleaning
both coil packs are working as they should

Everything appears to work as it should. I do smell coolant a little stronger than I should but I do not see any leaking around the head gaskets. Any ideas on what it could be? Generally whenever it does throw a code it is a "misfire on cylinder three" but it rarely throws a code. I am clueless and it is quite annoying.I want to get this issue resolved before I start adding some performance parts to my engine. Figured it would be a waste of my time to start improving it before all the basic issues are taken care of.

 

A year later and you still haven't figured it out?

https://www.f150online.com/forums/19...elerating.html

I think you need to think about a rebuild before you start thinking about performance parts.