Misfiring?

[Peter Arseneault]

I have a 2003 Jeep Liberty with the 3.7l motor. It's been sitting for a few months ( the battery actually drained down completely and was totally dead). I recently replaced the battery, and got it started up. Once warmed up and under throttle it seems to misfire, and runs rough. I've replaced the spark plugs, coils, air filter and verified no rubber hoses or vacuum lines are cracked.

I also did notice that if you put the vehicle in neutral, throttle it up, and let off the throttle that instead of returning to idle it stalls out and shuts down. There are no check engine lights and after a scan, no pending or active codes.

Any thoughts? Is it possible with the battery dead for so long that I have to do a throttle re-learn?

 

[LibertyTC]

Did you use #6987- NGK- ZFR6F-11G spark plugs set gap at .040 ?
Check with a VOM the alternator output voltage, what is it reading while running?
The IAC (intake air control) controls the idle & often the throttle body may need cleaning along with the IAC dirty & associated port all carboned up.
What brand of coil packs did you install? Mopar are the best, I got away using the standard brand.
Check all the coil pack connectors to ensure they are all plugged in securely.