02 4.3 loosing timing?

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by a.graham52, Jun 30, 2013.

  1. a.graham52

    a.graham52 New Member

    So I noticed today when pulling a hill from a stop and merging into traffic, 1st and 2nd pulls great. 3rd 4th and 5th lacked power pretty bad. My ultra-gauge showe engine timing going from almost 35-40 degrees of advance (at about 4500 rpms WOT) down to about 19 degrees. Then stayed around 20-25 degrees for the rest of the gears even with heavy throttle. Does this sound like a symptom of the crank sensor needing shims? Tomorrow I'm going to relearn the crank position at work. Any ideas?

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