What is causing my GMC to advance the timing about 25° when I plug the wire under the dash together?


Asked by Apr 28, 2015 at 07:25 AM about the 1995 GMC Sierra 1500 C1500 SL Extended Cab SB

Question type: Maintenance & Repair

I disconnected the tan/black wire before setting the timing. I set the timing to 0°. Shut it
down, connect the wire back, and when I check the timing, it advances about 20°. If I
disconnect the wire again, it goes back to 0°. Thanks for any help in advance!

1 Answer


when you set the timing to zero you are setting it at a starting point for the computer. Connecting the wire now allows the computer to manage the timing for optimum performance at all times

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