02 Liberty trouble HELP

Here is my story. 02 liberty limited 2x4 3.7 auto. At 106,000 miles had missfire with no codes. Took it to dealer they replaced lifters and cam followers for cylinder 2. Got jeep back. After 2 weeks presented with same problem. Took it back in they replaced all lifters and followers. Got the jeep back. Had for like 4 days and started missing with code p0356. Took back to dealer they said it was the ecm. Couldn't afford to have them fix it at this point. Ordered pcm from advance auto parts. Installed no change. Changed plugs. No change. Changed coil for cylinder 6. Started jeep ran a little better but still had a miss. Had scanned again. Now it shows p0351 changed cylinder 1 coil. No change. Dealer supposedly checked wiring and said it was ok. Any ideas I'm all ears. Cannot figure this thing out. Any help would be appreciated. Thanks

Run a compression check on all cylinders. I've had 14 '02/03 Liberty's over the last 8 months - all with bad engines. Miles ranged from 90k-170k. Most had a dropped valve seat (complete or partial) or a broken valve spring - usually it's the intake valve that is the problem. And YES I've had the seat drop then go back - which usually causes the rocker arm to fall off. I would also check the vacuum lines - look for the one off the MAS that connects to a "tee" next to the brake lines - the line is plastic with 5/16" hose as connectors - the hose hardens and cracks over time. These engines run crappy with vacuum leaks. Hope you locate the problem.

Would a vacuum leak or bad compression throw a p0351 code?

From what I've seen, the code is not always the problem, more the result. You could also have a bad cam or crank sensor as they direct the ignition. I know this all sounds odd, however I've had cylinder heads with an inch of burnt sludge inside them. The ends of the sensors were also sludged so they don't read properly. Does it run any different when cold vs. hot? Bottom line is these engines are very fickle and by no means perfect. They're like a book, you can't judge them by their appearance - it's what’s inside that matters. And yes, a bad valve seat would cause blow back through the intake to another cylinder, causing misfires.

Just something else to throw in. When u are driving if u keep if half throttle or so its not to bad. If you floor it its like hitting a rev limiter until u let of the gas then it will go again. If yoi don't let off the gas it will continue to slow down until you either stop or let off the gas.

Will it rev while in park - or just while under a load?

Will do it around 3000 rpm in park or neutral, will do it anytime you go over half throttle when in a driving gear.

I can think of many potential causes. I think a compression check is the first place to start. You should have at least 120psi per cylinder - 180 is ideal. If that all checks then test 1 thing a time. If compression is bad in a cylinder stop and look to replace the head. I wouldn't attempt to run it as they don't get better.
Another thing could be and I say could be is the knock sensors. They're attached under the intake and if they are failing they direct the ECM to change timing, that would cause the rev issue. I know of no way to test them. They plug in on the drivers side - back of valve cover. Try unpluging and replug. I'll keep thinking.

I will test compression tomorrow. And I will try to unplug and replug the knock sensors thanks for the info and I will update as I go

Your codes have nothing to do with the internals of your engine,you can skip any compression testing and plug changing as nothing done inside the engine will solve those codes.The knock sensors have nothing to do with those codes either so no use checking those as there under the intake manifold anyways.

Your whole issue is with the coils,wiring,or PCM.You need to carefully look at the coil connectors.Could easily be a bad connection.Could be the PCM that was installed is bad as well as the one that was taken out,it happens but more inclined you have a wiring issue from the PCM to the coil packs.

Does this happen during decceleration to a stop or at the stop?

Tested wires from ecm to ignition coil 1, wires both ohm out from connector to connector.

For the last post it does it on acceleration, for example, you take off and a going 25 miles an hour. You floor it and it will immediately act like it hits a rev limiter, will bounce the rpms but not accelerate any more until you let off the gas and then press it again. Anytime you go over half throttle it does the rev limiter type thing.

Sounds like a timing issue. Does it idle fine or a rough? Did you get a chance to do a compression check?

Has a miss at idle but rpms are steady doesn't go up or down. No my tester isn't long enough have to borrow one off a friend monday

Compression is good. Have voltage at the no 1 coil connecter. Order another new computer just to rule out that I got a bad one. Does anyone have a wiring diagram so I can check my wires from ecm to coil plug.

2005 jeep liberty 2.4L

#1 cylinder missfire, new plug, new plug wire,new coil,new c.e.m., new fuleinjectors and new vave lifters. no change still runs ruff at idel.:favorites68: any one know what to do next. charlie

dustinward03 said:

Compression is good. Have voltage at the no 1 coil connecter. Order another new computer just to rule out that I got a bad one. Does anyone have a wiring diagram so I can check my wires from ecm to coil plug.

Click to expand...

You can get a misfire from a bad injector.

You can get the 2002 KJ Service Manual here...includes the circuit diagrams:

Index of /manuals/Jeep/KJ

While you are measuring the wires from the PCM to the coil packs and injectors...make sure these wires are not shorting to chassis anywhere...if this is the case it will probably blow the PCM again so fix the short first then try another PCM.:shrug:

I had a misfire 'diagnosed ' as the cam sensors it wasn't simply the timing out a little :shrug:
proves codes are not always right and most mechanics follow what a code and computer tell them !!!!