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2005 Jeep Grand Cherokee Limited 4.7L Poor Idle Quality, Misfire
Posted to Chrysler Driveability on 10/27/2008 6 Replies

This jeep was just brought in to me with a rough idle, MIL light on with misfire codes and a B-1 downstream fuel system lean code. The vehicle will set either a random misfire or cyl 1,3 or 5 at idle only and the p2096 code after a 3 to 5 minute highway cruise after you decel and idle for about a minute. The local dealer had replaced the pcm, cyl heads, all coils and injectors and the "y" pipe with cats! I have done a visual inspection on the wire harness and wiggle tested, swapped the 2 downstream o2 sensors and removed the egr tube from the intake for testing purposes. The rough idle problem acts like a partially open EGR valve but that is not the case. I have smoke tested engine for vacuum leaks, Swapped the coils and injectors from bank 1 to bank 2 and inspected the inside or the fuel rail for any problems. Fuel pressure is a steady 58-60 psi and volume is strong. I drained the fuel tank and replaced with fresh, clean fuel even though it looked fine. Exhaust backpressure is near zero for both banks at 2000 rpm. The last thing for me to do is check cam timing on the left head. Engine running and static compression is all well with-in specs! One thing to add is the freeze frame for the p0300 always shows rpm under 300 when it sets the pending code. This is not the case as it never goes below 600. Any ideas or help would be greatly appreciated!

Related Repair History
Jeep just came from dealer. New PCM, Ign coils, Fuel injectors, Plugs, Both Cylinder heads and cat. converters!!

manifold Vacuum Readings
Idle: 18 in.
Cruise: 20 in.

computer Codes & Descriptions
p0300- Random misfire
p2096 - Bank 1 post cat fuel trim lean
FIX posted 11/3/2008

John from New Jersey

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car Vehicle Data

2005 Jeep Grand Cherokee Limited

VIN 1J4HR58N95
Engine4.7 L / 8 cyl / GAS
Trans5-speed Automatic (Electronic)
EmissionsOBD-II Compliant
SymptomsPoor Idle Quality, Misfire
OccursIdle, Intermittently

Trouble Codes

P0300Multiple Misfire Detected
P2096Downstream Fuel System Lean - HO2S-12 (Bank 1 Sensor 2)