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Discussion Starter #1 (Edited)
I have been having issues with my 7.3 on and off for a year. I had it die on me, replaces the low pressure fuel pump and cps and it ran again. It started 'missing', at an idle it will kill the engine, or at 60mph it will feel like it swallowed a cat (lurches) but keeps running. I now cannot read codes from the obd port.

I have checked all the voltages on the obd port (great thread on here) koeo and koer and everything checks out correct voltage on all the pins, continuity on ground and no shorts to ground. I had the check engine light turn on a couple times recently, and I cant read the code. Once I turn the key off the code goes away.

I replaced the ICP sensor (because the old one had oil comming through the harness) and no change.
I took the harness off the IDM and checked the impedances and potential shorts on all the solonoids after visually inspecting all the harnesses and moving them around while running. a couple came back really high (8 & 9 ohms). I had to move the truck, then pulled the valve covers and measured the impedance values on the pigtails, everythings fine. now the harness at the idm shows everything is fine. the one thing i didnt check before but looked at now is there is 5 ohms impedence between the injectors, not sure what that means or if its normal. but no continuity from the commons to chassie, and now the solonoids all measure 2.4 or 2.5 ohms. my vehicle has 375k mi and one solonoid is a different colour so im assuming it is all replaced at some point. untill recently I had no white exhaust on startup, now I do, if I plug in the block heater I dont, I have no grey or black exhaust.
Ideas?
 

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How does the engine react when you let off the throttle when driving? Smooth when moving and then rough when you let off? LMK
 

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Discussion Starter #3
How does the engine react when you let off the throttle when driving? Smooth when moving and then rough when you let off? LMK
the "miss" would happen arbitrarily when driving without changing the throttle.
When letting off the throttle it was smooth and wound down evenly.
Idiling was smooth and occasional misses would kill it in a moment, not prolonged sputter.
 

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How does the engine react when you let off the throttle when driving? Smooth when moving and then rough when you let off? LMK
the "miss" would happen arbitrarily when driving without changing the throttle.
When letting off the throttle it was smooth and wound down evenly.
Idiling was smooth and occasional misses would kill it in a moment, not prolonged sputter.
Ok that might rule out the IPR.
 

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Discussion Starter #6
any codes?
i cant read anything off the obd port, nothing connects, all the voltages and values on the obd port are fine and ground shows continuity. Occasionally a code populates (check engine light comes on) but i still cant connect to read it and it clears when the key turns off.
 

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Sounds like you have a bad connection on the injector harness - the UVCH gives a lot of trouble with the terminals when it gets old

Also sounds like your glow plugs are not working or at least some of them -- good idea to start at the glow plug solenoid and test the 12 volt side, then key on and check the output side, should be the same voltage on both large posts -- assuming you have the single large solenoid
 

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Discussion Starter #8
Sounds like you have a bad connection on the injector harness - the UVCH gives a lot of trouble with the terminals when it gets old

Also sounds like your glow plugs are not working or at least some of them -- good idea to start at the glow plug solenoid and test the 12 volt side, then key on and check the output side, should be the same voltage on both large posts -- assuming you have the single large solenoid
I did most of my testing from the idm connector to try and rule this out. Is this more of an issue when warm etc? Suggested solutions?
I do have the single post glow plugs. Ill check voltages tomorrow.
 

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i cant read anything off the obd port, nothing connects, all the voltages and values on the obd port are fine and ground shows continuity. Occasionally a code populates (check engine light comes on) but i still cant connect to read it and it clears when the key turns off.
The code is still stored in the PCM. Try to find a reader that will connect to a PSD.
 

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Im having a similar issue. When you lurch at 60mph does it almost die, stumble, respond to full throttle then blow out a cloud of blue smoke?
 
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