Hey guys, trucks been acting weird lately and I was wondering if y'all could help me figure out the problem....

I have a 98' F150 with a 4.6. Recently it has started missing when sitting still in D, R, etc. It does not do this when when in P or N nor when the RPMs is 900ish, only when sitting still with around a 600 RPM.

After it sits there for awhile it will begin to miss a bit, although not in any type of consistant pattern. When the gas is applied at all the problem goes away.


Does anyone have any ideas on what this might be? ANY thoughts/opinions/ideas are welcome


Thanks,

Jon

 

You are idling too low if you're at 600 RPM.

I'd suggest:

1) Cleaning the IAC valve

2) Inspecting for PCV vacuum leaks (although that usually sets a CEL)

3) Replace the fuel and air filters if it's been more than 30K miles

4) Clean the MAF sensor

5) Reset the PCM so it can re-learn idle strategy after doing the above. Remove the 3 or 5A minifuse in the add-on fusebox back in the corner of the engine compartment for 10-15 minutes.

Steve