How can I determine why my 1990 GMC Truck Sierra K3500 is backfiring?
I have a 1990 GMC truck Dualy K3500 454. It keeps backfiring. I need help to find what it
is that is causing this to do so.
454's were great work horses. With a lot of mileage the original simgle roller timing chain had a tendancy to jump a tooth in timing causing the backfire. Bring the engine to top dead center on the timing mark and then check the position of the rotor in the cap on # 1 cylerder. Let me know the milage