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P0300 Random Misfire with no luck pinpointing it.

15487 Views 47 Replies 9 Participants Last post by  mpardhal
Hello, first post, great info on here. I have a 2016 Versa Note with a P0300 code and running horrible. I replaced plugs, crank sensor, battery, made sure it had good fuel, replaced the intake gaskets, couldn't find any vacuum leaks, compression is good. What might i be missing? If i understand things correct, if it is a bad coil or fuel injector I should get a specific cylinder misfire and not a random code correct? Could a failing fuel pump be the problem?
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It still misfires. I hate this car....
This is a little out there, but is there any chance a rodent chewed on any of the wiring and something is shorting out - occasionally. Can you do a visual inspection of your wiring??

The reason I bring this up is... my neighbor had a large truck that was his tow rig for his camper. Mice or rats or some type of rodent made a meal out of some injector wiring, sometimes the wires would short out (going around a turn, hitting a bump, etc.) other times the current flowed, as the wires weren't grounding out.

I found the chewed area doing a quick visual inspection. As a test, I put liquid electrical tape on the exposed wire. Reset the ECM and had him drive it.. no more misfires. So he ordered up a new wiring harness as a permanent fix.
Thats a good thought, I never saw any chewed wires, but that doesnt mean there may be some wires that wore through the insulation. I'll have to chase the wiring harness and see if i find anything.
I have one other suggestion, but it is not free.
There are companies on ebay and for $100+/- they will test/fix your PCM/ECM and see if there could be anything wrong with the injector driver in the computer.
I've never used any of these companies, but since you have already poured a lot of money into the car, maybe another $100 to rule out the PCM/ECM may be worth the investment.
These companies can also VIN code a used PCM/ECM from a junkyard and you could swap in a different computer and see if the misfire still exists??
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