Nissan Repair: 1995 Nissan Pickup 2.4L 4x4, distributor shaft, shaft seal

Question
My 1995 Nissan Pickup, 4x4 with a 2.4 liter four cyl has 77000 miles on it. Recently it started to seem to be severely under powered from when I originally got it, it was also missing and burning oil, however it only did this intermittently. Thinking it was electrical I replaced cap, rotor, wires and plugs, as well as my fuel filter, all to no avail. I brought it into a local shop, and they found the timing was out by twelve degrees. This seemed to fix the problem, and for the next month or so it was fine, with significantly restored power. However after a short time parked, it has started backfiring and missing when I’m not on the throttle hard (but still have my foot on the gas) (i.e., going down hill) and it smells like there is unburned gas in the system. At idle it will run nice and strong, then suddenly my rpms will drop, and it will shutter and just hang on without stalling. This all ONLY happens after the truck is warm, and thus far, I have lost no power from when it came out of the shop. The odd thing is again, when the truck is cold right after start up it runs strong and smooth. My check engine light has come on twice but only for about ten minutes a time, and then it fluttered out. (Both times it appeared only when I was coasting with little acceleration pressure) I am at ends as to what’s going on, if you have any ideas, let me know! Thanks so much, Tim

Answer
Tim,

Sounds like the ignition is cutting out after the truck warms up.  I would check to see if the distributor is contaminated with oil.  With the years and miles the distributor shaft seal usually fails and allows oil to walk up the shaft and onto the optical shutter wheel and the LED pickup and receiver.  This means that the engine will cut out and backfire and then come back.  Usually, this is associated with the vehicle being at operating temperature since the oil has to walk back up the distributor shaft.  Well, that is my suggestion given what you have documented.  I bet the code for the check engine is related to crank angle sensor since that is what the distributor is in your truck.