2004 V8 misfiring code

I have a 2004 envoy xl that is misfiring. It started off real subtle about 6000 miles ago. It seems like a heart that was fluttering. When it'd happen I could just hit the gas and it would clear out right away. It is now happening all the time and is throwing a misfiring code P0300. I have had it in a small shop and they replaced the mass air flow sensor ( I think). It started misfiring right after I picked it up. I figured I'd take it to the dealer and I was charged $359.00 (so far) for fixing a chafed wire. It drove good home but the started misfiring again.
I printed off a page from this website about a guy that had a 2004 XL that had a cracked gas tank filler tube that was a factory recall. The dealer said that does not apply to mine, he thought it was electrical. I don't know if he checked the fill tube or not we'll see.

anyone out there have an idea?

thanks,

Welcome to AF . The cracked tank will cause a code for an emissions issue not a misfire, first I'd get my 359.00 ineffective repair money back. The list of possibilities for a random misfire code is lenghty at best, there is no quick answer. The truck should be checked for freeze frame info when the code was set and misfire counts checked, wire, coil, injector, plug are just some of the possibilites, but the dealer knows all this.

i sure would go get my money back..they never fixrd it so you don't owe them a dime.like mod. said the dealer no's just what's wrong with it.get it fixed right..good luck...

the dealer called me and said there are plastic clips on the injectors that were missing. the previous shop had taken them off I guess. The dealer says they can't do anything until these plastic caps are back from the previous shop. The previous shop I took the envoy to found them but said they would not be an issue with my problem?

Maxwedge somethimes I wonder if the dealers should be reading forums like this. Nice name also I have a 69 charger. Much easier to work on.

Thanks all and take care,

Agreed, the retaining clips for the injectors, unless a fuel leak was generated, would not cause this issue, the dealer can get them thru their parts dept. BTW, we had a 68 Charger RT and used it for a tow car back in the day, where is it now? LOL