Is there anyone that can help me out there? I have a 2004 Jeep Liberty with a 3.7 that has a P0300 multiple miss fire condition that is going on right now that is really got me stuck! I have pulled all 6 coils & checked the resistance & they all read 1.0 to 1.1. I have checked the resistance on all of the injectors & they all read between 14.5 & 15. I have replaced all of the plugs. Went to replace fuel filter from Autozone & come to find out that there is not one on this one after dropping the fuel tank & seeing that it has one return & one pickup line. the fuel filter from Autozone had 2 pickup lines from the tank to one supply to the engine. I did a fuel pressure test & I got between 65 & 70 lbs. I then pulled each coil 1 at a time & on cylinders 1,2,3 didn't make a difference on how it ran. I pulled all 3 at the same time & it didn't make a difference. So I replaced the coils & the fuel injectors on 1,2,& 3 & it still runs like crap. I did reset the computer because I read something about if the computer doesn't see voltage on the coil it will shut down that injector. Still no good. It is not backfiring through the throttle body or the exhaust. when it is idling & missing there is no funny sounds. when you idle it up to 2000 RPM's it has a funny little ticking sound that sounds like a pushrod on an old chevy coming loose but, it has overhead cams. The wife went to the gas station & filled up & 20 miles or so down the road is when this all started happening the next day. If it was bad gas why would it only be missing on 1,3 on the drivers side & 2 on the passenger side? Any help would be great. Baffled in Illinois.
2004 Liberty P0300 Multiple Misfire
- Thread starter HALL JP 2
- Start date
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Snail Farmer
Full Access Member
Any other codes? My P0300 ended up being caused by O2 sensors. Only use NTK (NGK) O2 sensors.
libertybob
Full Access Member
Thrown Rocker Arm?
3.7's and 4.7 v8's can throw the rocker arm out from under the cam thereby de-activating a cylinder. No codes. May or may not make a noise. Problem is hydraulic lash adjust not keeping pressure on rocker arm. Look up on the net. There are a couple of videos on YouTube about this.
3.7's and 4.7 v8's can throw the rocker arm out from under the cam thereby de-activating a cylinder. No codes. May or may not make a noise. Problem is hydraulic lash adjust not keeping pressure on rocker arm. Look up on the net. There are a couple of videos on YouTube about this.
I'd get the thing scanned (good scanner) and see what the data tells you. Sounds more like an O2 sensor to me too but seems like you'd get a code specific for that too.
Probably not a rocker, mine threw a cylinder specific misfire code both times and was pretty obvious but it was an exhaust rocker. Luckily it fell out of the way both times. You already said no backfire out the intake, which is what mine appeared to be doing. I heard a person lost an intake rocker and very bad things happened to the cam. Not sure what would happen if an intake fell off but didn't hit anything.
Lash adjuster definitely could cause falling rockers but I'm more inclined to believe mine is a sticking valve that takes the pressure off the rocker then it slides out.
Compression check is a good idea.
