Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

454 tbi backfiring

Discussion in 'The Garage' started by 89Burben, Aug 13, 2005.

  1. 89Burben

    89Burben Registered Member

    Joined:
    Jan 3, 2005
    Posts:
    98
    Likes Received:
    0
    Location:
    CT
    its and 89 suburban with a 86 454 remanufactured motor with about 35,000 miles on it. i changed it over to tbi with all of my 350 stuff. the truck has ran descent for about 11 months now. About 4 weeks ago i pressure washed under the hood and drove it to my buddys house and on the way there i noticed at WOT it backfired through the exhaust pretty badly. on my way home form there it didnt do it anymore. then that week we made a 400 mile trip to PA and it was also fine during that trip, meaning no backfires. About 2 weeks ago it starts this backfiring thing again. Except it was backfiring through the tbi and the exhasut during driving under a load. since then i have replaced the coolant temp sensor, distributor, icm, esc, map sensor, egr, spark plugs, plug wires, cap, rotor, recent tbi rebuilt, changed the fuel pressure regulator anyways, fuel filter, coil. the fuel pressure is fine when driving (checked with a gauge) and its not throwing any codes. everything seems to be working....The only thing i have not done is drive it and make it backfire with the scanner plugged in. this prob is occuring outa both banks, but the pass side more prodominatly. whenits in park it runs good but when i rev it up to 3,500 rpm the tach shows that the rpms are jumping up and down around 250 rpm but the motor is running smoothe. i have the tach wire hooked up to the test wire off the molded plugs for the coil. if someone could please help this problem has me stumped...
    thanks brian
     
  2. 89Burben

    89Burben Registered Member

    Joined:
    Jan 3, 2005
    Posts:
    98
    Likes Received:
    0
    Location:
    CT
    ok i checked the timing chain. is 8-10 degrees of slack normal? or is that timing chain shot?
     

Share This Page