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missing engine


RW

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I have a 99 Sierra 5.3 that has a minor, but annoying problem. It has for want of better word a constant miss. It is noticable when ever I am running at a steady cruising speed. It is most noticable at highway speeds with CC on. It even showed up when I had the truck dynoed. I have had it to 2 different dealerships with no satisfaction. One said the new engines were supposed to run like that, the other after 3 days said they couldn't find a problem. Miraculously it reappeared on the way home. I figure it is either fuel or ignition timing related. My Autotap software indicates my igniton timing degrees are all over the board when I am running on the highway. It ranges from 22 to 46 degrees and the graph looks like a seismograph during an earthquake. This is at a steady highway speeds. If it is the timing how do you fix that on these new computerized trucks. Any suggestion would be appreciated. I am trying a third dealer Monday.

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I wish I had an easy answer for that. You could be right that the timing variation could be causing the "miss" that you are feeling, but the computer constantly adjusts the timing in repect to many inputs from the sensors on the engine, it could be trying to compensate for something else that is giving it a faulty reading. check the other info available with your software and see if any other readings don't seem right. EGR problems can cause problems like this too. Good luck with the third dealer.

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