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vintageduramax
06-02-2009, 14:21
hey guys,new to this so bear with me.I just bought an 05' gmc (my 2nd duramax)and been to dealer twice already for 2 problems,they fixed 1 (#7 injector rattle) but the other one they have no idea.what it does is if you are idling in gear and just barely put pressure on acc. pedal it will start missing-so everytime you take off from a stop the truck shakes until it gets past it,it seems to be worse when cold but still does it even at 210,
sounds like injector to me but they say they can only do balance test at idle,also no check engine light.any ideas welcome-THANKS !!!!!!
truck only has 52,000 miles on it.
DmaxMaverick
06-02-2009, 15:37
Welcome aboard!

What you are experiencing is an injector balance issue. The injectors only enter the balance mode with less than 1% APP input (throttle), which is why it's smooth at idle, and not-so-smooth off idle. The balance rates can only be read at idle (0% APP), but will indicate how much the injectors have to compensate (balance) to smooth the idle. You will need a capable scanner to read the idle balance values, which is much more than just the balance rates.

If your engine is very rough off idle, you have significant issues that need to be addressed. If it's slight, a fuel additive with injector cleaner may help. If you have access to a Predator programmer (it doesn't have to be "locked" to your truck), read your balance rates and PWM values, and post them here. We can help with some preliminary diagnosis.
vintageduramax
06-02-2009, 16:21
thanks for the reply DMAX,i was not sure there was a programmer available to the public to read these areas,have been using stanadyne for the last 4-5 tanks and it may be a little better-but not much,it just kills me when you can show the dealer what it's doing and they tell you they & tech don't know how to fix it.i think they are being lazy,other than this issue i love the truck!! have you seen or heard of this before-because these guys seem dumbfounded
!
DmaxMaverick
06-03-2009, 00:29
Seen it before, a few times. Each time, one or more injectors were replaced to cure it. Your dealership is either playing dumb, or they truly are. You might try another dealer. It is still under warranty, and you are owed a good running truck.

It could just be a fouled injector. Try some SeaFoam. I haven't used it, but hear good results have been had for fouling.
vintageduramax
06-03-2009, 08:27
thank you so much for the reply !! I will let you know how it goes.