After reading all the posts on this problem and seeing the same pattern it would seem to me that the problem is in the EGR system.
I am thinking maybe dirt or something has got into the EGR passages ??
Fireplug
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Originally Posted by markdpro
My 97 Yukon has this set of problems. Same engine. The intake manifold gasket started to leak coolant and the dealer pulled off the fuel system to replace it. When I got the truck back( with a new oil pressure sender, water pump and spark leads $1500 total) I had a little induction growl on throttle opening but unless the radio was off I couldn't hear it(can't hear much anyway says my wife) On a fishing trip many weeks later, I pulled my boat up a long hill. The initial throttle up works very well. strong pull and no miss. Its when I back off at the crest of the hill that the miss occurs. The first time it happened I was on cruise but I can reproduce the effect every time I go to a high throttle situation and back off. When I come back on the throttle I briefly have a heavy miss.
My latest fishing trip has escalated the symtom with a flashing check engine light on the initial throttle up but still no miss until the throttle down throttle up cycle as the load is reduced.
Like everyone, I need reliability and I'm worried about getting stalled somewhere but my fear of the dealer's costs and my doubts about their abilities keep me looking for a diagnosis before I try to fix this.
I do all routine maintainance and have replaced the fuel filter and pcv valve and installed new plugs. I also have an OBDII code reader and there are no codes present.
I'm wondering if the heavy load heats up some component that causes preignition in the multiport Fuel injection throttle body. Combined with a vacuum leak could that be the problem?
I'm at the point of abandoning GMC forever. I have a seven year old truck with 54 000 miles on it garage stored and carefully maintained and I am losing trust in it's reliablity
I really appreciate your ideas cause I really need a fix.
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