HELP!! popping & backfire, starts great, irratic idle. 97 silverado z71 5.7 Vortec
I just bought a 1997 chevy z71 with vortec 350 its backfiring real bad. it cranks and starts fine though. i have changed plugs, wires, distributer and no change. I have checked the egr and pin 1&5 reads .01v and the pins 2&4 is reading 3,4v. I have checked the MAF, it seems good. I have no specific codes but cleared anyways. What flashes is the catalyst heat monitor, catalyst monitor and egr monitor. Im very mechanically inclined however this has me baffled. It popps and popps, sounds like its popping in the exhaust, the engine does not surge or misfire but occasionally lets out a huge gunshot like bang. prev owner said he blew out a cat baffle. I would usually just start replacing the sensors in a process of elimination but these sensors are pricey. codescould it possibly be a stuck valve and making it backfire through the intake? I'm at a stand still here.
Last edited by mrcleanmom; 06-17-2011 at 11:18 PM.
Reason: title unclear so I included some symptoms so I can maximize help