cycling ignition resets misfire??????

[sscb]

Thanks to all the posters here. Many times you have helped me diagnose and fix an issue simply by reading.

This one however has me confused.

2002 V6 - 220000Km's

Repeatedly throwing a P0304. Misfire on #4. Also sometimes a "misfire on engine start"
Engine is obviously running rough. CEL flashes which I believe is Limp Mode?
Been down this road before.
Changed ALL the plugs and COPS (they only had 50000Km's on them since last time) and the upper intake gaskets (learned that one the hard way)

Here is the strange part. I can be driving, engine missing, CEL flashing. I pull over, turn engine off and then back on and the misfire is gone.
CEL stops flashing goes solid, engine runs smooth. I can clear the P0304 and the CEL does not come back on.

At this point if I let the car sit overnite (or for a full 8 hour workday) I'm right back at square one with the rough running engine.

So I'm thinking engine temp has a part to play here?
And possibly someone smarter than I can offer insight as to how cycling the ignition fixes a misfire issue?

Other than that I guess Im chasing a bad injector or a MAF sensor issue?

Appreciate any help.

SSCB

 

[joegr]

What brand of COPs?
No, flashing check engine light does not indicate limp mode. It indicates misfire. It flashes to let you know that this is serious as damage to your catalytic converters is being done, and it is also possible to damage the rings and cylinder wall on the misfiring cylinder. Flashing check engine light = stop driving.
The PCM detects misfire clearly enough that it cuts fuel most of the time to cylinder #4, to reduce the damage being done. You cycle the key off and back on, and it goes back to injecting fuel all the time until it detects the misfire again. You're not "fixing" anything. You are just masking a symptom.
It could be a bad injector, or just the connection to it. It's unlikely to be the MAF, as it shouldn't then be consistently #4 only the misfires.

 

[sscb]

Thanks for the clarification joejr.

I will proceed with testing the suspect injector.

sscb

 

[RigsLS]

Test coil 4 to 3 see if same error or follows, also firmly check connectors/wiring.

 

[sscb]

Just wanted to close the loop.

Was indeed a bad injector on cyl 4.

Thanks for those who took the time to respond.

SSCB