I recently started getting rough idle. It started while driving on the highway when I slowed down to a stop idle was pretty bad. After reading a lot of post I replaced MAS original from bputah , magnecor 8mm wires, Bosch +4 plugs, bosch o2 sensors all 4, induction cleaning. Idle is still rough and getting codes for misfire on cylinder 1,3,5,7. Runs strong just has rough idle. What can be wrong? Vac leak? The truck had a whistle sound when at idle for a few weeks but went away haven't heard it anymore.

 

Idle is controlled by the IACV (Idle Air Control Valve), it can be cleaned with carb cleaner. Yes, a vac leak would cause problems, because it represents air entering the system that has not gone thru the MAF (Mass Air Flow), and that is called un-metered air.

 

Yes I cleaned the idle valve seems to work good, when cold idle is high then goes down when warm. I will try to look for a vac leak any suggestions where most vac leaks happen

 

Another possibility is that your coolant temp sensor is off the reservation. With a scanner, mine shows ambient temperature when parked under the shade tree. Unplugged, it shows -40F. The computer will throw more fuel at the problem because it thinks you are in northern Alberta instead of the 7000 block of Biscayne Blvd (known for serious mechanics as engine blocks must be taken inside nightly).

 

Where is that sensor located

 

Check the temp and it is working. Going to try looking for vac leak

 

Thanks for the help. Found the problem bolts were loose on throttle body near the heads. Tighten them up and put it back together and idle is smooth