Nissan Repair: 2001 Pathfinder Misfiring, defective coil, shaft seal

Question
QUESTION: I have a 2001 Pathfinder that has blown a fuse 3 times in 2 years.  This kills the engine.  It is a 10-amp, red fuse.  Simple enough fix, but now the fuse didn't blow and the idle became rough and the check-engine light was flashing.  I took it to a local shop that determined that 2 of the 6 coils had gone bad, so all were replaced.  Same problem - cylinder 5 misfires.  New plugs, same problem.  New wires, same problem.  New injectors, same problem.  Cylinder compressions are all 110 to 120.  Then on a test drive the pesky fuse blew.  What's left to replace?

ANSWER: Bob,

I am pretty sure your Pathfinder has a distributor?  If it does it is most probably the optical shutter wheel under the distributor cover.  Number 5 is not getting proper reference signal and it is causing the misfire problem.  Now, be sure to change the coil from another cylinder to number 5 to make sure you did not get a defective coil.  But, from my experience the optical shutter wheel gets coated with oil when the shaft seal begins to fail and this messes up the works...  The fuse is another problem and I would be looking at all battery cable connections and the grounds on the block to the frame and firewall.  I even put extra grounds on the engine to get better, and shorter signal time for the sensors.  There are grounding kits you can purchase, on-line, that eliminate most problems like the one you describe.

---------- FOLLOW-UP ----------

QUESTION: Thanks!  I am going to look for those issues on my own as my bill at the shop has exceeded my funds.  After I sent this they did find one interesting thing: apparently there are three wires going to each coil.  They found that one wire going to cylinder 5 caused a misfire when it was jiggled.  Further investigation determined that the wire was broken inside the perfectly normal looking cable.  Now it works.

On a separate question: Any idea why I am getting so much heat when I set the temp to 66 degrees?  65 is all cool air, 66 and up are very hot.  Any idea where the sensor is?

Thanks again,

Bob

Answer
Bob,

Cool and I am gland that they found the problem.  Second, the bend door is probably sticking.  I wouls get under the dash and look how the door moves when you turn the temperature up and down.  It should move proportionally with the control.  My bet is it is sticking and when you get to the temperature you list it ends up moving all the way to hot.  Either it is out of adjustment or hanging.