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Cuts out, jerks intermittently, code P0300

(2003 Jeep Grand Cherokee)
in Steamboat Springs, CO on August 10, 2009
My 2003 Jeep Grand Cherokee jerks and cuts out intermittently after running for 45 minutes or so. Over the last month my tech has replaced: fuel filter& pump, one oxygen sensor (has 4), crank position sensor. Now showing code P0300 but it won't run rough when the tech drives it and he said he can't diagnose the problem. I've taken this to two shops and they are tired of seeing me!
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Popular Answer
on August 10, 2009
Possible Causes Setting Conditions
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 Induction system (e.g., in the intake manifold)
Check for air leaks in the EGR Vehicle 2001 Jeep Wrangler 4.0L, Vin S, Eng Cfg L6

Customer Concern: The engine continues to reset misfire codes P0300, P0301, P0302, P0303, P0304. The engine runs great. The coil rail and Crankshaft Position (CKP) sensor have been replaced.
Tests/Procedures: 1. Run Top Engine Cleaner (TEC) through the engine to clean carbon from the valves.

2. To prevent carbon from building up again, drive the vehicle slightly harder.
Potential Causes: Carbon Fouled Valves

Tech Tips: The 4.0L engine needs at least 3500 RPM for the exhaust valves to rotate. The engine needs to be driven hard enough to keep carbon from building up on the valves.
Diagnostic Codes: P0300, P0301, P0302, P0303, P0304, P0305, P0306
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 (e.g., coil, spark plug or boot) in multiple cylinders
Vehicle driven with low fuel pressure or while very low on fuel
Engine speed less than 3,000 rpm; adaptive numerator updated, and the PCM detected a multiple misfire rate over 2% (2.5% for ULEV models), then this code sets in 2 trips. If a 2% misfire rate is detected at engine speeds above 3,000 rpm, it sets on the 1st trip.

This code sets in 2 Trip(s).
This code will turn on the MIL (Malfunction Indicator Lamp)

I really believe you need to have a complete fuel injection service down. I mean in rail clean. this a company that I strongly recomend that you find a shop that uses these products. The website is
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