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Keoweekat

99 ISC Cummins 8.3 Skipping

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We have a 99 ISC 8.3 in our Navigator on a short trip we were going through the mountains and using the exhaust brake at the bottom of one hill I turned the exhaust brake off and started pushing the throttle pedal and there was a dead miss on one cylinder and it was blowing smoke for about 1 mile then the smoke cleared up but a dead miss was still there.

I contacted Cummins and said it was probably an injector and said it was fine to limp back home about 60 miles.

How do you isolate the bad injector or would it be better to take it and have it put on a computer.

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Just pulled the valve cover and discovered that both valve plates that the rockers push that sets on both valves for the #2 cylinder were off and laying inside and the intake push rod was bent. All 4 valves move smoothly they were not stuck or seem bent. This happened as we were using the exhaust brake I was wondering if this could have caused this, I'm ordering 2 new push rods and putting it back together and I want be using the exhaust brake until that is checked out. Sure hope that's what caused the push rod to bend.

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The ECM on your engine should have set a code. You should be able to read it using the check engine light and the switches under the dash next to the steering column.

You should check or have a mechanic check the valve train settings. There is a specific method and clearance to set the intake and exhaust valves. Having the rocker arm come loose on the 1 cylinder, could mean that others are loose also or out of spec.

Rich.

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Agree with Rich.

While over-speed can cause this, so can way-out of adjustment valves. Check all of them.

Other than high RPM, I can't see how the exhaust brake back pressure could cause this IF it is set to proper PSI for your engine . You can check with your exhaust brake manufacturer or Cummins for exact maximum PSI backpressure for your specific engine.

I know PacBrake has a port on the side of the brake where you can attach a fitting, hose and gauge so that you can drive with the gauge attached, use the exhaust brake and verify maximum PSI backpressure.

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