Can P0301 code be related to bad injector

[randerson0248]

I have a 2001 Pathfinder with high mileage that is misfiring under light load. Half or full throttle will cause the misfire to go away.

The only code is P0301. Sometimes P0300, instead of P0301.

Coil on cylinder 1 seems to be operational when I check it.

Also, cylinder 1 has bad piston rings and burns oil. Is it possible that the injector on cylinder 1 is carboned up and causing the misfire code?

It seems that P0300 - P0306 would normally indicate an ignition problem. Is that always the case, or could my problem be the number 1 injector.

Thanks

[NismoPick]

Step 1: Pull, check, replace spark plugs. Use NGK's.
Step 2: Replace fuel filter.
Step 3: Use a QUALITY fuel treatment additive through a tank of gas.

And yes, a gunked up spark plug can cause a misfire.

[4xq]

Well, the fuel injector is actually up in the intake manifold. Just as the intake valve opens, it squirts fuel, which mixes with the air that gets sucked into the cylinder. The injector can be carboned up from deposits left by gasoline if it has been a long time since your injectors have been cleaned. Grab a couple of bottles of Techron and run them through your next two tanks of gas for that.

Your spark plug could be oil fouled ( unburned oil in the cylinder) or carbon fouled (deposits caused by burning lots of oil in the cylinder). I would probably try a new spark plug first as that seems likely given your bad rings problem on that cylinder.

So, put a new plug in it, then clear the codes, and see if P0301 goes away. P0300 is random or multiple misfire, and that may be an indication you need plugs all around.

After that for p0300 you start getting into bad coils, bad crank sensor and more complicated stuff. I'd try the maintenance items first and see if you get lucky.

[4xq]

I see NismoPick posted while I was typing - sorry for the repetition.

[NismoPick]

I see NismoPick posted while I was typing

Great minds n such. Your post is more detailed.

[4xq]

Could be - I have an 88 735i in the garage. Sadly, on last legs.
The 81 280Z is nice.

[randerson0248]

Thanks for the replies.

I have already changed all the spark plugs and cleared the code (PO301). Code returned.

I have eliminated (I think) ignition as the cause of of the PO301 code. My question is can an injector problem that causes a misfire set the PO300 series code? Or is the PO300 - PO306 only for ignition misfires?

[4xq]

P0301 - Cylinder 1 Misfire Detected:

Possible causes
- Faulty spark plug 1
- Clogged or faulty fuel injector 1
- Faulty ignition coil 1
- Fuel injector 1 harness is open or shorted
- Fuel injector 1 circuit poor electrical connection
- Ignition coil 1 harness is open or shorted
- Ignition coil 1 circuit poor electrical connection
- Insufficient cylinder 1 compression
- Incorrect fuel pressure
- Intake air leak

Thats a cut and paste. I would add crank sensor also.

I would move the coil to another cylinder and see if the misfire code follows the coil just to rule it out. If I remember correctly 2001's had coil issues.

[Chuck Tribolet]

On the 2001, #1 cylinder uses a different coil pack than the other five, so you can't swap.

I suspect you are getting oil fouling on the #1 plug.

Chuck

[randerson0248]

I'm back to working on this one again.

40 psi compression on #1.

I plan to hone and re-ring cylinder 1, unless the bore is damaged too much.

Am I better off pulling the engine, or can I remove bank 1 head and oil pan easier than removing the engine.

Manual says to remove engine for head removal.

Thanks.