cylinder 4 misfire!

srosario

srosario

New member
so jeep beach was awesome, coming back another story. On sunday one hour in to the 6 hour drive and check engine light. p304 & p300 ( misfire cylinder 4 & multiple misfire). changed the sparkplugs and rotated the coil packs and still the same.
Tomorrow to the dealer, after doing some searching on the forum im taking it to the dealer. Hopefully could get it cover under powertrain. wish me luck

pick of the plugs and number 4
IMG_1402.jpgIMG_1396.jpg


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Did you reinstall double platinum champion plugs back in and did you gap them to .048-.053?
 
srosario said:
i installed denso
View attachment 256637


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Click to expand...

The spark set up on our Jeep is called a waste spark set up. So it fires a spark to cyl 1 by going from the center electrode on the plug to the side electrode. Now when the spark jumps that gap the motor acts as a ground and actually transfers that energy over to cyl 2 and has the spark jump the gap in reverse from the side electrode to the center. It is EXTREMELY important that you use double platinum plugs on our Jeeps because of this. Iridium plugs should not be used and can actually damage the coil pack due to them requiring a higher firing voltage.

Your cyl 4 misfire could have been plug related but you need to have the root cause found. It's companion cyl is #3 so there could be an issue with #3 wire not allowing the plug to get the proper voltage to jump the gap or something else. Hard for me to pin point it over the forum.

I hope the dealer is able to figure it out for you
 
So Steve ,
Which brand do you recommend to use?
I am about to hit 50k miles it is time to start thinking about changing
 
Andy5160 said:
So Steve ,
Which brand do you recommend to use?
I am about to hit 50k miles it is time to start thinking about changing
Click to expand...

I recommend whatever comes from factory. In my case its champion double platinum in the 3.8. I would assume that it's the same plug in the 3.6 motor.
 
ok got the truck back,
they replaced the #4 cylinder head and and the seal in the breakdown.

Glad everything was cover under powertrain.

update:
supposedly the dealer changed the oil and filter, after driving it home check the oil level, and its a 1 quart low.
so decide to do and oil change to mobil 1 seens they use non syntetic. Drained the oil and its my same old oil and my STP extended performance filter. crazy


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