2004 Liberty - Misfire Mystery

jeep
liberty

#1

Codes:
P0305 - Cylinder 5 Misfire Detected
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
P2314 - Ignition Coil E Secondary Circuit

Symptoms:
Runs rough, and shakes at idol;
Low power/acceleration;
“Stutters” (stalls but recovers) when you mash the accelerator too fast;

I Changed the coil and plug on cylinder 5. The Same codes and symptoms persist.


#2

here’s the very next thing you do . . .

Perform a compression test

dry test, followed by wet test

Please report back with the numbers


#3

Okay. Do I just need to do cylinder 5, or should I check them all?
This might take some time, as I’m going to have to get a tester and a deep-well connector.


#4

Do them all


#5

Always do a dry compression test first.

This lets you know if any of the cylinders are low on compression.

Then when you do a wet compression test, this lets you know if a cylinder is low on compression because of worn rings.

Doing it the other way around requires that you wait til all the oil seeps past the piston rings.

Then if you find a cylinder with low compression, then you want to perform a leak-down test to determine why the cylinder has low compression.

Tester


#6

If you google that code, you will find several instances on Chrysler vehicles. One poster fixed it using OEM spark plugs, another by repairing the wiring from the PCM to cylinder 5.