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Massive power loss pulling hills - Paccar MX13 455

Paccar MX 13 455

When I down shift from any of my high side gears more so when loaded at 30-44,000 lbs I get a miss fire or chugging from my motor. I lose all power climbing hills of all sizes (don’t feel it as bad on flat land) and once I’m back into 13th gear and feather the accelerator, I can feel the miss fire feeling go away.

The only code is for #4 injector. Saying it’s weak. But only had 1 hit on that code.

Dealership was not that concerned about the #4 injector.

We did swap rocker box with #3 rocker box to see if problem follows.

Did overhead adjustment.

Dealership’s like to see at least 3-4 hits on a code before checking out the problem. Is what Allstate Pertbilt told me.

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Hello I'm having the same issue ive replaces the #5 injector and did the overhead adjustment…i was wondering if you had fixed your problem if so plesase let me know. Thank


Sorry for the late response. After replacing numerous sensors, unfortunately the problem has not been fixed.


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I would say check the wiring to that injector first, then turbo actuator

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Britt will be eternally grateful.
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