engine misfire po306

Has anyone had this problem, My dealer reprogrammed the computer the about a month later I get PO306 code, I beleive they cracked a plug or damaged the coil, I knew I should have done it but it was under warranty. now I find out I know more about the problem than the so called tech. that worked on it.

Has anyone had this problem, My dealer reprogrammed the computer the about a month later I get PO306 code, I beleive they cracked a plug or damaged the coil, I knew I should have done it but it was under warranty. now I find out I know more about the problem than the so called tech. that worked on it.
They could not crack a plug or damage a coil by reprogramming the bcm or pcm, what was the original problem, do feel a noticeable engine miss? Lots of info missing here. What do mean " I knew I should have done it"?

They could not crack a plug or damage a coil by reprogramming the bcm or pcm, what was the original problem, do feel a noticeable engine miss? Lots of info missing here. What do mean " I knew I should have done it"?

A tech was under the hood, the truck was in for the po306 code, which according to my scanner is #6 cyl. misfire, my wife took it in to the pryor okla. chevy dealer, the paperwork says he reprogrammed the eprom, don't know but the truck does not run as good as it did before she took it in. so now That it is out of warranty by about 100 miles they don't want to be of any service, yes I have called chevrolet customer service, waiting on their response. I am taking on the task as I am a fleet service manager so this is not new to me just another quirk of this truck. since my post I have removed the plug and coil pack an installed them in seperate cyl. just to see if I get the other cyclinders to misfire. yeah I know: you think hes a service manager why go that route, because I cannot use state bought equipment for my personal use without being prosecuted, so back to my less informative handheld monitor, any way I was just wondering if anyone else has had this problem and what their outcome was, I know the problems just trying to repair inexspensively I really hate using dealers for repair.

update to this, Like i said in my post should have fixed it myself, finaly got it back from the dealer in pryor oklahoma, they said it was fixed, next day same code, so i did a leakdown check and compression test myself, cyl's 1-5 read 230psi #6 reads 130 leakdown test confims a valve is leaking into top end, pulled head off. 1 exhaust valve in #6 is loose, further investigation reveals the valve seat has dropped and guide is shot. so machine shop gets head and guess what chevy does not have the guide or valve seat available yet, as does any aftermarket source, Thank you MORITZ machine in tulsa oklahoma and Terry Dixon in Vinita Oklahoma for the repair terry sent the head to moritz they custom made a new seat and guide and did the whole valve job thing and now the engine runs better than it ever did, and get this if you goto the autozone, o'reillys etc, the fel pro head set is around 300 bucks, chevy dealer is actually cheaper at 148 bucks, head bolts are the same price at either place. end of story thank god now I am off to trade it in on a new mustang!

update to this, Like i said in my post should have fixed it myself, finaly got it back from the dealer in pryor oklahoma, they said it was fixed, next day same code, so i did a leakdown check and compression test myself, cyl's 1-5 read 230psi #6 reads 130 leakdown test confims a valve is leaking into top end, pulled head off. 1 exhaust valve in #6 is loose, further investigation reveals the valve seat has dropped and guide is shot. so machine shop gets head and guess what chevy does not have the guide or valve seat available yet, as does any aftermarket source, Thank you MORITZ machine in tulsa oklahoma and Terry Dixon in Vinita Oklahoma for the repair terry sent the head to moritz they custom made a new seat and guide and did the whole valve job thing and now the engine runs better than it ever did, and get this if you goto the autozone, o'reillys etc, the fel pro head set is around 300 bucks, chevy dealer is actually cheaper at 148 bucks, head bolts are the same price at either place. end of story thank god now I am off to trade it in on a new mustang!
Good diagnosis, good work in general very smart doing a leak down test. I still don't know why since it was in warranty during your visit when they failed to diagnose the problem, that you didn't pursue this thru the courts, or at least push the dealer for help, as a former GM SM, I would have done something to pay for this for you. This was a tough job on this engine labor wise and an obvious defect. Check on alldata.com for a tsb issue on this, thought I may have seen one there.

That was some good diagnosis work! Thanks for the follow-up. That's the first valvetrain issue I've heard of with the 4.2L I6. I'm sure the dealership that originally looked at it did not even consider a loss of compression induced misfire. They probably never saw it before. I would make some calls to that dealership, write some letters, etc.. to see if they would reimburse you some of the cost. They owe you something for the knowledge alone! Pursuing this thru the legal system would cost more time and money than the repairs.

Joel

That was some good diagnosis work! Thanks for the follow-up. That's the first valvetrain issue I've heard of with the 4.2L I6. I'm sure the dealership that originally looked at it did not even consider a loss of compression induced misfire. They probably never saw it before. I would make some calls to that dealership, write some letters, etc.. to see if they would reimburse you some of the cost. They owe you something for the knowledge alone! Pursuing this thru the legal system would cost more time and money than the repairs.

Joel
Not in small claims court for breach of warranty.

well I did contact chevy customer service6 seperate times, and 2 dealers my original dealer where the truck was purchased, and vinita cheverlet, the original deal changed ownership and could not to seem to find any paper work on my purchase, I purchased this vehicle through a voucher program, my brother in law works for a gm subsidary that makes catalytic converters, I got a heck of a good deal, since they are 45 minute drive I pretty much told them to take a hike since they were not going to be much help, Vinita did offer to pay for the parts and I pay labor, thing is I already had the parts and the labor charge quoted was around 1500 bucks and they told me it would be a 24 hour job according to there labor book, next stop my lawyer now he gives me a quote I do not like I said heck with it I'll do it myself, since I am a certified aircraft mechanic, heavy equipment and watercraft and motorcycle mechanic this should be no problem, plus my current job is overseeing the fleet maintenance for a correctional facility, Hmmmm same job as my counterpart at the dealer, Long story short it's fixed my total cost outlay is $508.46 and 1 lost saturday from doing any honey do's, wife's happy she has truck back and as long as she is happy the world is just fine, but I will not buy another gm product unless it is an old muscle car like my 69 ss 396 chevelle, so hope this info helps anyone with a similar problem the only outward signs were a loud ticking like a stuck lifter, (the engine had hardly any noticable loss of power) and the misfire code, I did read on another area that gm washaving head gasket problems, that is what i was hoping I had but the leak down said otherwise. thanks to all