Today while driving to work I nailed getting on to interstate and at 400RPM I starting getting a real bad miss that made a sputtering noise and bog.When @ idle it has a slight miss that goes in and out for about a second than straightens out.I only have 21000 miles on my 03 GMC 5.3.A MONTH AGO THE DEALERSHIP changed the lifters on the drivers side.What do you think they may have done wrong.I ran good for about a month now the *****.I tried changing fuel filter for the hell of it with no avail.I am putting it back in dealership Monday and would like to know your oppinions on this so I can go in with loaded guns if they try and bullshit me.I was going to start my install tommorrow on my Yank,servo and cooler.Good thing it happened today so I won't have to worry about my warranty.

 

what type of gas mileage are you getting? One time I broke a wire loom on another car and had the spark plug wires sitting on the headers...which caused the car to miss really badly and have no power. Does your engine feel like it is surging? It could be any number of things, dead valve is a possibility. either way, at 21,000 miles I'd demand a crate engine from the dealer.

 

13.8 miles per gallon on last tank.usually I get 16 or 17

 

sounds almost exactly what happened to me. i had sucked an intake gasket in the dealer said. let them check it out. they fixed the problem in a couple hours

 

Thanks sportside,I feel a little better about that scenario compared to a bad valve.keep the opinions coming guys,I only got till Monday.I will post results when I get it back so others may be able to use this info.

 

Unfortunatly for things like that, its almost always where someone had their hands last. To replace the lifters they had to pull the head so the list of what they missed or did wrong could get long. Let us know what they say and good luck.

 

I would double check coils and plugs for the side they worked on. Remove the plugs and look at them. They could have cracked one. I cracked one during my head job. If you have EFIlive, you can see misfires by cylinder. That was how I was able to find.

 

Got my truck back today and all I can say is ****** RIGHT!The dealership found a bad coil on #5 cylinder.They reflashed my 03 with an updated 04 program and my truck runs better then it ever did.When I kick it down at 30 it instantly downshifts to first with no hessitation at all like it used to.Throttle response is as good as it was when I had the UPD on.Now it is time to reinstall hpppiii and UPD to see.In a couple of weeks I may find time to install my Yank,servos and cooler.If my tax return gets here soon enough I may also get in on GP from NELSON.Then it is of to the track!