01 4.8 detonation

[Z28TWITCH]

This is a new Tahoe in the fleet. Driving the other night, went to juice it getting on the highway and it kind of fell on its face around 5krpm and started pinging/almost rattling real bad, came off the go pedal and the check engine light starts flashing. Code was a pending P0303. I swapped that plug and wire with cylinder 1 and still got P0303. The truck is tuned with a handheld so I reverted to stock and even threw some 93 octane in the tank...still there. Fuel issue? Bad valve or spring?

 

[Scottydoggs]

sounds like a bad cat or two maybe. the clogged cat can cause a misfire, and bang around if its broken up inside.

 

[Z28TWITCH]

Cats dont rattle or get unreasonably hot. Tried cleaning the maf with no luck. Any other ideas?

 

[Kraig]

Does it have a dead cylinder? Try swapping the injector or start looking at mechanical issues—compression test, leak down, etc.

 

[Scottydoggs]

i just had a coil die on the o5 3500 work truck, it never showed the code for #8 that had the dead coil just a p0300 and ran like crap.

started pulling plug wires off the coils looking for the spark to jump, all sparked but 8, took 8 off and swapped it with 6, now 6 failed to spark and 8 did. so bought a new coil runs like new again.

oddly enough at the same time it tossed a coolant temp sensor code as well. p1258. it seems that code means the pcm is disabling 4 injectors, so it was really running bad like that with a misfire lol

so worth a few minutes to pull plug wires for a quick coil test. i pulled them wires off truck running, bare handed, didnt get shocked lol

 

[Z28TWITCH]

Truck doesnt run bad at all. It has 108k on it. At idle it has a slight stumble but nothing outside of what Id call normal and no symptoms at part throttle. Compression test is where I was going this weekend because I suspect a lifter of valve spring. Guess Ill find out.