4.0 liter, will only run with throttle depressed. Showing a cylinder 5 misfire only. Seems to me that it would idle with just one cylinder missing. No other codes. Should I replace plugs and wires and go from there? Thanks

 

it only has 40k on it.

 

If you have a misfire, you should definitely address it. However, I would suspect the IAC valve or possibly a vacuum leak for the idle issues. Another possibility is rodents building a nest or storing food in the air intake blocking air flow (suspected since a 2001 with 40K sounds like it's been setting up a lot). You can check for vacuum leaks by spraying starting fluid around the intake and listen for engine speed variation. The IAC can be cleaned by removing it and spraying throttle body cleaner into the IAC and into the intake ports.

 

Ok. Thanks. I guess the big question is.. can the IAC be bad and NOT throw a code?

 

Yes. Dont know if that is your problem, but yes.

 

Great! Thanks! That was my first guess all along, but I didn't realize that it would not always throw a code. Thats what confused me.