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Missing at idle. Been to 3 shops $4800 later...still no fix


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Our shop has a test box that will plug directly into the VP pump and it allows you to run the engine at idle and high idle, i dont know what the exact rpm's are but it basically just tells you if the problem is mechanical or electrical. If its mechanical then it should still run bad whereas if it electrical then it should run normal. I think it would be beneficial to locate one to try.

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Think sledwrecker is onto something. I did find this while running around, might spark some more thoughts.

The Camshaft Position Sensor (CMP) on the 5.9L diesel engine is located below the fuel injection pump. It is bolted to the back of the timing gear cover. The Camshaft Position Sensor (CMP) contains a hall effect device. A rotating target wheel (tonewheel) for the CMP is located on the front timing gear. This hall effect device detects notches located on the tone-wheel. As the tonewheel rotates, the notches pass the tip of the CMP. When the leading edge of the tonewheel notch passes the tip of the CMP, the following occurs: The interruption of magnetic field causes the voltage to switch high resulting in a signal of approximately 5 volts . When the trailing edge of the tonewheel notch passes the tip of the CMP, the following occurs: The change of the magnetic field causes the signal voltage to switch low to 0 volts . The CMP provides a signal to the Engine Control Module (ECM) at all times when the engine is running. The ECM uses the CMP information primarily on engine start-up. Once the engine is running, the ECM uses the CMP as a backup sensor for engine speed. The Crankshaft Position Sensor (CKP) is the primary engine speed indicator for the engine after the engine is running. With the clip on the sensor pointed up, the far right terminal with the switch on should produce 5 volts, the middle pin should produce ground and the far left pin should show continuity to the 24 pin on the C1 ECM Connector. I would start with the basic wiring diagnoses to verify the wiring is correct.

On top of the items we've covered here's some items that can also cause CMP codes. * Injector DTC's present * Other DTC's * Camshaft sensor * (F855) 5-Volt supply circuit open * (K916) Return circuit open * (K44) Signal circuit shorted to ground * (K44) Signal circuit shorted to supply (F855) circuit * (K44) Signal circuit shorted to (K916) return circuit * (K44) Signal circuit short to voltage * ECM * Intermittent condition

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  • 3 weeks later...

OK guys just wanted to give yall an update. We pulled the cam out and the cam had been walking forward about an 1/8 inch. It had been rubbing against the timing cover!! So we got it repressed on and i have now drove it about 3000 miles without one issue. Its so nice to have my rig back! Thank you to everyone who was there to help!! :hyper::woot:

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OK guys just wanted to give yall an update. We pulled the cam out and the cam had been walking forward about an 1/8 inch. It had been rubbing against the timing cover!! So we got it repressed on and i have now drove it about 3000 miles without one issue. Its so nice to have my rig back! Thank you to everyone who was there to help!! :hyper::woot:

this makes since if im understanding it right, if the cam and gear walked forward and being the gears are helical cut, it would throw the cam off time by a little bit that would make the idle rough.
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