Mechanics

ROUGH IDLE THROUGHOUT RPM RANGE

1991 Jeep YJ • 4 cylinder 4WD Manual • 112,000 miles

My 1991 Jeep Wrangler 2.5L runs rough through out the power band. At idle through to 3 to 4k plus RPM is an intermittent miss. I have changed plugs, ignition wires, dist. Cap, rotor, fuel filter, fuel pressure regular, and coolant temperature sensor. I have pulled the O2 sensor from the manifold exhaust pipe and there is no change in the way it runs. The injector o-rings have been replaced as well. I have pulled the fuel rail and injectors and cleaned them the injectors with Seafoam per their website. Fuel pressure should be in the 32-38lbs range. The "inexpensive" fuel injection tester gauge I purchase shows 55lbs. I put this on my daughters 4.0L and it read 54lbs so I believe the gauge reads high. I have searched for vacuum leaks with no success. I placed the vacuum gauge in place of the fuel filter to check the fuel pumps reading. Key on 30lbs, while cranking 40lbs, and while idling 50lbs. It will hold pressure of 30lbs after the engine is shut off in excess of 15 minutes. To top it all off it shows codes of 12 (recent battery disconnect), 33 (open ac circuit(non ac)), and 55(end code) which are all normal for this vehicle and expected.

Any thoughts or suggestions is greatly appreciated.

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Ddross60
February 4, 2011.



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