hi there im new to the blazer forum familer with others. im working on a friends 04 blazer. 1st problem was it wasnt starting he said he just put new plugs wires cap and rotor. found out that he didnt put the rotor screews in so that taosted the rotor. fixed that ran fine. cpl weeks later he says it just died on the road. got to looking at he truck got it to run revs bouning up and down 0 -700rpm open the throttle it backfire and die. took out the o2 sensors thinking the cats were clogged. changed the ckp sensor. nothing new dizzy and guts new ignition module. did not replace map sensor. i appear it have spark but not out the dizzy still. checked all my fuses im gonna go back with a test light today and check again. ive replaced everything that had to do with the running poorly to begin with cap, rotor, dizzy, ckp . and still there is nothing i believe the ecu is working because its still showing me a sevice engine soon light. any ideas for blazer vets. also i have no cominucation with the scan port?ecu?

 

Get the SES light code read and let us know what it is, but it sounds like a timing issue.