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02 Mountaineer Misfire / Bucking / Backfiring

skizzlez

New Member
Joined
October 8, 2011
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City, State
Wisconsin
Year, Model & Trim Level
02 merc mount awd 4.6l
Hello everyone,

Long time lurker, but have come to the point with this truck that I must ask a question. My father in laws truck (the 02 moutaineer in question) has been giving me a rather large headache.

Without giving a 3 page post about the problem, I will try to sum it up in a few bullet points immediately. Followed by a more "thorough" description of what I've done to diagnose/attempt to fix the problem.

  • 02 Mountaineer, 82,000 miles
  • Symptom 1 - 3 months ago it began - Single cylinder misfire number 6
  • father in law brought truck to mechanic
  • mechanic replaced plugs, and coil pack
  • mechanic checked compression - cylinder 6 = 120 psi, all other 7 cylinders = 170 psi
  • mechanic abandoned vehicle

So, this is where I began.
  • Removed heads
  • diagnosed bad valve guides (worst was cyl 6)
  • had my machinist do a complete valve job
  • reinstalled everything (new gaskets all the way up
  • various other new unimportant things (belt, starter etc)

Started the truck, noticed motor shakes in engine compartment during idle. Not terribly, still revs fine, but definitely has a random misfire. I checked the compression. I now have 170 on ALL 8 cylinders. Previous experience pointed towards coil packs. So, I replaced a few that I thought didn't affect the idle when I removed them. All in all, I replaced 4/8 of the coilpacks. STILL has problems. I also replaced the camshaft position sensor as I heard that causes this problem.

SO, here is my current issue. Please let me know what your thoughts are.. I'm thinking PCM or timing ??

  • The motor shakes randomely at idle
  • you can feel a distinct misfire under load between 2000-3500 RPM
  • the misfire seems to get worse as the truck warms up
  • I have had the following codes re-appear since the head job + CMP sensor


• P1309 - Misfire Monitor Disabled When the misfire monitor is disabled, usually due to the input signal generated by the camshaft position (CMP) sensor, by sensing the passage of teeth from the CMP wheel.
• P0351 - Ignition Coil A Primary/ Secondary Circuit Malfunction Each ignition primary circuit is continuously monitored. The test fails when the PCM does not receive a valid IDM pulse signal from the ignition module (integrated in PCM).
• P0340 - Camshaft Position (CMP) Sensor Circuit Malfunction The test fails when the PCM can no longer detect the signal from the CMP sensor.
• P0301 – P0308 - various cylinder misfires


Thanks again, sorry about all the text..... I know it sucks to read this much.

cheers,
Jason
 






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