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Good Afternoon,

A few weeks I took our high mileage (278,000ish kms) Jeep to the track in Edmonton for western mopar madness. We ran 8 passes and got pretty consistent 13.8’s in the 1/4 and I was pretty happy. We packed up the truck and headed home; after hour 2 or the 3 hour drive home in torrential rain the sky’s cleared and I stepped on it to pass a car. That’s when I let off the engine started to misfire. I took the first ramp and limped it to a parking spot where it stumbled and died. I restarted it and pulled code P0303 P0300. Now I just had Magnaflow 16423 race cats put 3 weeks prior and the shop installed the upstream o2’s down stream and it acted the same way then. So I just had it towed home.

The following weekend I swapped in spare coils, injectors, all new 02’s , crank and cam sensors and nothing changed other then I only got p0300 codes. Still ran like @$$ And the bank 2 cat was glowing hot. I did a propane enrichment test for vacuumed leaks nope.
Ok time to dig deeper; I pulled plugs and did a compression test, all cyl were 155ish except #3 and it had Zero, zip nada the big O. Ok now we are getting somewhere, down went the camera and short of a ton of carbon build up everything looks ok. Then the leakdown,... air flow was on rotated the engine air came out the intake and as the engine rotated it stopped but the exhaust did not. Ok toasted valve.

But what I am curious on is why if bank one cyl 3 is down why was bank 2 stupid hot? Why did one valve cause a p0300 and not the P0303? It “feels” like more than one cyl down but the scan tool and basic tests tell me other wise.

Am I missing something or is there an inherent issue with the 6.1 or simple old age/mileage?

Thanks
 
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