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Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 26423
Experience:  ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector
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In addition to my 2004 Overland, I have a 2005 Grand

Customer Question

In addition to my 2004 Overland, I have a 2005 Grand Cherokee Limited with the 4.7 v8 with 155k. We've had an ongoing issue with cylinder misfires. Initially, P0308, then 0306, and now it is P0308 and P0303, or sometimes just P0303. Plugs, coils, injectors
and various sensors have been replaced. Compression tested and fuel pressure tested. Dealer flashed reprogrammed. Just had brand new cats, with 02 sensors and cat back exhaust installed. Vehicle is now running better (before the new cats, o2 sensors and exhaust,
it was running really bad), but still getting P0308, and P0303. And once we go over 40, the throttle is not steady (for example, accelerating onto a highway, you can fell this slight surging of the throttle). Ran the code reader, and now have P2097 - never
have seen this ever before.
Submitted: 2 years ago.
Category: Jeep
Expert:  Amedee replied 2 years ago.

Thank you for requesting me! I have seen a lot of cylinder misfires on this engine due to many things. The misfires could be caused by coolant leaking into the cylinders or carboned up valves. However, I dont have a listing for the P2097 code. Are you sure this is the right code?

Customer: replied 2 years ago.
I got it twice (cleared the 1st time). I googled it and it said it was "poor catalyst fuel trim"
Expert:  Amedee replied 2 years ago.

This is a rich code. It indicates that the engine is running rich on bank 1.

Customer: replied 2 years ago.
what would cause it to do that?
Expert:  Amedee replied 2 years ago.

This code comes from the oxygen sensor reading. If the engine is misfiring, the oxygen sensors are not going to be reading correctly. You need to get the misfires fixed first. However, to answer your question, rich running engine along with misfire codes could be leaking injectors.

Expert:  Amedee replied 2 years ago.

Also, bad oxygen sensors can also cause the engine to run rich as well.

Expert:  Amedee replied 2 years ago.

Oxygen sensors can also cause this slight surging condition while driving.. also a stuck open EGR valve

Customer: replied 2 years ago.
It has brand new 02 sensors, installed last week with the cats/muffler.
Expert:  Amedee replied 2 years ago.

Thats good! I would disregard the rich code for now and focus on the misfires. Diagnose the misfires first and then go after the rich code if it continues