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awestbrook 07-30-2013 08:27 PM

misfire problems. pls help!
I have a 2003 Jeep Liberty 6cyl 3.7. It starts to misfire while going up hills on the highway (usually around 60mph or higher but has misfired just giving it too much gas going uphill at lower speeds). We would have to pull over, turn the car off, restart the car and it seemed fine until we again gave it too much gas going uphill again. We took it to auto zone to have them diagnose. Originally, it showed a misfire in cylinder 6. So I changed the spark plug and coil pack for #6 but it continued to misfire the same way. The father in law said it sounded like the fuel pump or fuel filter so they had both replaced. Car seemed to work fine for a few weeks (and I try not to push it hard up hills. plus turn the overdrive off going up hills seems to help a little) but began to misfire again. Again, we had to pull over, turn the car off, restart and everything seems fine. We have been taking it very easy (or as easy as I can when I have to drive 100 miles a day for work on a highway with lots of hills) and the engine light has remained on for the last month but no misfires until today. So we took it to auto zone and now its coming up with misfire in 6 & 3. Again, all we had to do is pull over, turn off the car, restart and it seems fine if we take it easy. So the spark plug & coil pack for #6 has been replaced along with the fuel pump and fuel filter, oil change/lube job was done recently, ive tried the injector cleaner that you add into the gas and I always use regular unleaded gas. When the fuel pump and fuel filter was replaced, the replaced the radiator since it was leaking. Recently getting an oil change and lube job, we were told we also have a small leak in the front differential. Also, throughout this entire thing, it has also popped up with a code for random misfire and something potentially having to do with the timing chain (cant remember what code that was though). Any ideas? I tried to provide as much info as possible. Please let me know if you need anything else.

GilbertF 08-01-2013 05:53 AM


I may not be the coils or plugs, check the cylinder by doing a compression test to see if it internal problem.

You can perform a vacuum test to test the intake gasket and the erg.

Here is what a misfire all can be.

ASD relay output circuit to the ignition coil or injector has high resistance
Base engine mechanical problem that affects multiple cylinders
Check for air leaks in the Air Intake system
Check for air leaks in the EGR system and in its related hoses and/or valve
Check for air leaks in the PCV system and in its related hoses and/or valve
Erratic or interrupted CKP or CMP sensor signals
Fuel delivery component fault that affects two or more cylinders (e.g., a dirty, contaminated or sticking fuel injector, fuel filter clogged, low fuel pressure)
Ignition system problem (coil, spark plug or boot) in two or more cylinders
Vehicle driven with low fuel pressure or while very low on fuel

Please let me know if I can be more assistance to you.

sosyj 08-06-2013 06:46 PM

I recently ran into a similar problem with a GM 5.3L. Turns out I had water in the fuel rail. It would collect in the rear going up hills a cause misfires. Pulled the tank a found a couple of pints of water. Good luck!!

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