Random Cylinder misfire

FLgator

Test Drive
Location
NE Houston
hello once again all,

Have a code that came up, P0300, or a Random/ multiple misfire in multiple cylinders. New NGK iridium spark plugs were put in, along with NGK spark plug wires a couple weeks ago for a tune up. Anyone have any other clues?

Thanks.
 

Bushnut

First Fill-Up (of many)
Check the rotor and cap.... while checking the rotor look inside the distributor for any red dust or excessive play of the shaft. The distributor is known to go bad.
 

FLgator

Test Drive
Location
NE Houston
Check the rotor and cap.... while checking the rotor look inside the distributor for any red dust or excessive play of the shaft. The distributor is known to go bad.

Would the distributor cause a severe vibration that runs throughout the vehicle during idle?
 

Bushnut

First Fill-Up (of many)
No. That is the miss fire. Unbalanceing the engine. When all 6 cylinders fire in the proper order it purrs like a kitten, when one or more don’t fire that causes the uneven vibration.
By checking the rotor and cap look for excessively burned contacts. Or a build up of carbon on them. If that is what you find, replace them This is the cheap fix.
If everything looks ok. I might start looking at the fuel delivery system. Excessive or not enough fuel can also lead to misfires.
I had this problem with an R50 pathfinder. It had a leaking injector that flooded one cylinder causing it not to fire. Once I replaced that injector it worked fine. If this is the problem just hope it is on the passenger side as it is easiest to get to. Driver side requires the removal of the intake plenum to access the injectors.
Good luck, you can fix this.
 

Will O'Brien

Test Drive
My list of things to check:
1) eyeball the plugs for discoloration. Mine had one that's black and the rest looked great. Could be a bad plug as well.
2) compression test, much easier if you pull that intake.
3) Could be a bad injector.
4) Could be bad/leaky fuel pressure regulator
5) worn distributor
6) timing - check it.
7) old timing belt
8) MAF - can provide bad info on air flow and screw up AFR
9) Vacuum leaks - cracked intake hoses can also throw off AFR

Usually the last two come with other codes like o2 (that's my experience on other engines, not this one however)
 
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