2004 Liberty misfire

[Cpdyer08]

Hello all, I’m new to the forum. Having issues with my 2004 Liberty. I have a 2004 Liberty with the 3.7, and I’m getting the P0305 misfire code. It idles rough but runs fine at higher RPM. I bought a scanner that reads live data, and the bank 1 fuel trims seem pretty off. STFT at idle is around -6% and LTFT bank 1 is around -10.5% at idle. Bank 2 seems much better with both being roughly the same pretty close to zero. After a short ride, the pending 305 code comes up and the trims are even worse on bank 1, STFT at -10.8% and LTFT at -18.8%at idle. While driving the bank 1 trims are much much better, it’s just at idle they are bad. I know this means the computer is leaning out the bank, the scan tool also gives me a little red flashing circle that says EVA on it for the evap. Is it possible that there is a vacuum leak in the evap system somewhere, or could it be more of a fuel related thing since it’s only one bank? This thing has a lot of new parts on it and I don’t just want to keep replacing things that have no effect on it. Also the compression on bank 1 is 145,150,150. Thanks in advance

 

[LibertyTC]

P0305 = Cylinder #5 misfiring. Start with the basics.
Do you have the correct spark plugs in the Jeep?
NGK- ZFR6F-11G are the correct plugs only & gap .040 inch. Many issues can be fixed with correct plugs.
^Spark plugs should be replaced every 35k miles.
Clean the IAC and port, carbon build up and effects idle etc.
Coil packs, Mopar is best & are wires to coils connected properly?
Using a Fuel pressure gauge, what are the readings from the shrader valve at fuel rail?
Key on psi reading is? Running psi? Leak down reading after 15 min engine off?
Evap-spray throttle body cleaner around any suspected lines/ intake does rpm change?
Next may be # 5 injector issue?

 

[Cpdyer08]

P0305 = Cylinder #5 misfiring. Start with the basics.
Do you have the correct spark plugs in the Jeep?
NGK- ZFR6F-11G are the correct plugs only & gap .040 inch. Many issues can be fixed with correct plugs.
^Spark plugs should be replaced every 35k miles.
Clean the IAC and port, carbon build up and effects idle etc.
Coil packs, Mopar is best & are wires to coils connected properly?
Using a Fuel pressure gauge, what are the readings from the shrader valve at fuel rail?
Key on psi reading is? Running psi? Leak down reading after 15 min engine off?
Evap-spray throttle body cleaner around any suspected lines/ intake does rpm change?
Next may be # 5 injector issue?

Thanks for the reply. The Jeep has new coils, new champion copper plugs which have always been run in it gapped @.040 new cam sensor, crank sensor, swapped injectors around. Fuel pressure is good and steady. I did not do a leak down. I am going to replace the IAC because it looks pretty ******, I also cleaned the port. I have smoke tested the cylinder in question and also the vac lines and intake and found no leaks. I’m beginning to wonder if I have a valve issue, it’s weird because the problem it as idle, otherwise it runs fine and has plenty of power.

 

[Billwill]

Thanks for the reply. The Jeep has new coils, new champion copper plugs which have always been run in it gapped @.040 new cam sensor, crank sensor, swapped injectors around. Fuel pressure is good and steady. I did not do a leak down. I am going to replace the IAC because it looks pretty ******, I also cleaned the port. I have smoke tested the cylinder in question and also the vac lines and intake and found no leaks. I’m beginning to wonder if I have a valve issue, it’s weird because the problem it as idle, otherwise it runs fine and has plenty of power.

I would first follow the advice given as regards fitting the correct NGKs gapped properly. Champion is a respected make but I have seen so many posts on all the Jeep Forums about this problem with the Gassers that get resolved by fitting the NGKs!