spamhater

I had just got it out the shop for the fuel guage and pump. Little did I know the mechanic unhooked the battery while working on it. So my computer had not finished learning the settings yet. I drove straight from the shop to meet the guy who was buying my truck. I did notice some predetonation while accelerating so I stopped and picked up some octane boost. I had been running a lower octane so I know I needed it. Well once I meet him, he saw the truck and loved it. Things went well until the test drive. The buyer didnt know much about performance trucks so predetonation wasn't in his vocabulary. He drove it a while under normal load and it was perfect. I told him he wouldnt get the full effect until he punches it. Well he did and the detonation started and got horrible. I couldnt tell him fast enough to let off and then it happened. One of the cylinders went out and the service engine light started flashing. Well we went back to his truck and he went home. I restarted the truck and the light went away but it left a noticeable tap behind. I stopped at autozone and read the code which was cylinder 7 missfire. The truck seems ok now except for the tap. Looks like I'm keeping the truck for now. Does anyone know if that is a cylinder tap or something in the heads making that noise? Whats my next step now? I guess my 09 GMC will have to wait.

Sorry for the long write up. Just trying to explain the whole thing.

sickREDsierra

iTrader: (17)

i am trying to understand why you would run LOW OCTANE fuel in a modded/supercharged truck?

i would NEVER do that. its hard to blame someone for doing something to it that you told them to do...

as for the tapping/pinging, could be quite a few issues.

Tootall

iTrader: (79)

pull the plug on that cylinder . . .

meaning pull it out for inspection

Torque_Wrench

iTrader: (13)

Yeah, I'm going to have to ask why you ran low octane fuel in a modified truck? Adn what kind of tune were you running? Just disconnecting the battery should have only reset the fuel trims, if I'm not mistaken. The PCM will settle in while at idle after a minute or so. Did the tech re-flash your PCM or update it or something?

spamhater

The thing is, I never run regular fuel. I always run supreme but every once in a while I will put plus, the medium grade and only adding to the half a tank of supreme thats already in the tank. This truck is my dailey driver so I very rarely get on it anyway. I've been driving back and forth to work for the last year in it and it's only 3 miles from my house. There isnt even a place to go fast anyway. I've been trying to conserve for a while now. Why it detonated that bad? I'm not sure. It's never done that before. Thats why I think it was because of the computer being reset. And I never blamed the guy for my mistake anyway. I wasn't mad at him. He knows that too.

spamhater

The tech should not have did anything to my pcm. I do know he disconnected the battery though. The only tune I have is the tune that came with the radix. When I purchased it, I told them all of the mods and they sent the programmer to me. Since then, I havent changed anything. After work, I will pull the plug and look at everything. I hope I dont have any serious issues with it. I'd hate to have to tear the motor down.
If the PCM resets at idle in just a few minutes, then there could have been other issues then. Now I know it ran just fine (no pinging at all) when I dropped it off at the mechanic. I noticed the pinging afterwards.

outlawz2004

iTrader: (18)

The mechanic may have been out hotrodding it.

Neil 6.0

Did the shop drain the tank for the fuel pump change? If so, what kind of gas did they put back in it? Maybe the new fuel pump is a POS causing it to run lean?

krambo

iTrader: (4)

If the tech did that, he should be responsible.

viciousknid

iTrader: (8)

Good point. GO back and ask the tech if he put low octane fuel in it, or if he test drove it.
Great example of things to ask before leaving the mechanic with a beast like that.