First time poster, but I've visited here often.
I had an unusual condition with my son's 05 Liberty with the 3.7 last winter where when the ambient temp was 30-40F, It would misfire. Engine operating temp had no effect. It misfired when cold at the beginning of a trip and was misfiring at the end and would show p0300. Warmer days it ran perfectly. This cold season and it was now misfiring at 50 degrees so I had to figure this out. I replaced the right O2 sensor and it was the same. Changed plugs, rotated coil packs, ran injector cleaner and changed the crank sensor and the misfire remained. Bought a vacuum leak smoke tester and on a warm day, there were no leaks other than the throttle body. Tried it again on a cold day and there it was. The O rings on three of the fuel injectors were pushing smoke. I got new O rings and let me tell you, the OG ones were fossilized to brittle plastic, New O rings in place and no vacuum leaks and the lean condition was gone. It was 35 degrees this morning and no misfires so I'm considering it fixed for now.
I just wanted to post that since I searched a while and never read anywhere that injector O rings leaking could create a vacuum leak that resulted in a lean misfire. I hope it helps someone else.
I had an unusual condition with my son's 05 Liberty with the 3.7 last winter where when the ambient temp was 30-40F, It would misfire. Engine operating temp had no effect. It misfired when cold at the beginning of a trip and was misfiring at the end and would show p0300. Warmer days it ran perfectly. This cold season and it was now misfiring at 50 degrees so I had to figure this out. I replaced the right O2 sensor and it was the same. Changed plugs, rotated coil packs, ran injector cleaner and changed the crank sensor and the misfire remained. Bought a vacuum leak smoke tester and on a warm day, there were no leaks other than the throttle body. Tried it again on a cold day and there it was. The O rings on three of the fuel injectors were pushing smoke. I got new O rings and let me tell you, the OG ones were fossilized to brittle plastic, New O rings in place and no vacuum leaks and the lean condition was gone. It was 35 degrees this morning and no misfires so I'm considering it fixed for now.
I just wanted to post that since I searched a while and never read anywhere that injector O rings leaking could create a vacuum leak that resulted in a lean misfire. I hope it helps someone else.
