Have a 2001 4.3 l s-10 blazer, it spit and sputtered and shut off, while trying to start it , it was acting like the timing was off,,popping through TBI. i have it a garage and they thought it was the timing chain and it wasn`t.they change cam sensor, crank sensor , they have spark and i sprayed starting fluid in the TBI and it still wont start, it backfires or sometimes shoots flames out the TBI,,and also is there a spire unit in a TBI engine ? can you help me please!