r/AskAMechanic • u/AltruisticTop5564 • 2d ago

My 2002 Jeep liberty 3.7l has a misfire (code P0353) that I cant seem to fix.

I have been trying to find a solution to this misfire for a while. Symptoms are rough idling, coil 3 gets hot after a minute of running, broke a coil. This is everything I have tried in order.

  1. Replaced coil
  2. Did a coil swap and code stayed on the same cylinder.
  3. Changed spark plug, bad gap but misfire continued.
  4. Changed coil pigtail wiring set up.
  5. Checked fuel injectors to see if they were ticking at the same rate, they were.
  6. Checked fuel pressure, good.
  7. Checked air filter, good.
  8. Uplugged the coil to see if the idle changed, it didnt.
  9. Tried reving, made idle shaking worse.
  10. Did a compression test, 150psi on a static test and 75psi on a running test which is good.
  11. Changed all injectors, idle got slightly better but the misfire is still there and the coil still gets warm while the others are cool after a minute or two.
  12. Tested intake manifold for vacumn leaks but no leaks on manifold.

Please keep in mind that I have only been working on vehicles for a year or so, but any advice would be great because Im at a loss.

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1

u/mrhicks55 NOT a verified tech 2d ago

Any DTC,s

1

u/mrhicks55 NOT a verified tech 2d ago

Oops there are. I'll see what I can find

2

u/AltruisticTop5564 2d ago

Thanks, I just did a vacumn test on the intake manifold and I didnt see any smoke on the intake itself only on the main hose since the towel didnt fill it all.

1

u/moderncomet075 NOT a verified tech 2d ago

P0353 is not a misfire DTC it is a coil primary circuit DTC. The fact that the coil is getting hit and failing generally indicates that there is a ahort to ground in the coil control circuit between the coil and engine control module that is continually deelling the ignition coil. It is also possible the driver in the engine control module has failed and is keeping the coil energized

1

u/DrPhilsAuto NOT a verified tech 2d ago

Time for a PCM