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  1. #1

    Angry 94 Chevy 350. Back fire through TBI

    Okay guys. I'll go ahead and list what I've not done. I've not replaced the crank and pistons. Other than that. Everything from the Camshaft to the TBI itself is new. Brand new. Coil, plugs, dizzy, fuel relay, fuel pump, filters, cam, lifters, cam bearings, push rods, spark plugs, all plugs for the wiring harness. Fuel line, fuses, Throws no codes, shows no check engine lights. When I'm driving, around the range of 40MPH in 4th gear the motor will back fire through the TBI every now and then. I hit 50MPH, throw it into 5th and it will do it literally every 3 Mississippi seconds without fail. I changed the valves first, then bought entire brand new heads not rebuilt, still did it. Replaced cam shaft/lifters and push rods next due to believing it had a worn lobe. Did nothing to help. After that I basicly restored the old rust bucket with replacing every single little thing that has anything to do with the way the motor runs. And still does it. I love this truck. Truly do. But I'm at the point I'm about to take it to the beach, put it in 1st and 4 low, throw a brick on the gas and drop the clutch and tuck and roll. Then enjoy watching it go for a very deep swim. I've dumped enough money into it that I could have just bought a crate 350 and been done with it. Only thing I could possibly think of is taking off the converter because it might be clogged *though seein as it's hollowed out, I don't see why it would be* Help me please, before I start to think it's getting thirsty.

  2. #2
    Sr. Engineer
    Join Date
    Oct 2010
    Location
    Indianapolis, In
    Posts
    493

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    I cannot remember the exact details but another member had a sympton like yours and eventually found a screw that had come loose in his distributer and was bouncing around and causing a missfire. Check the mechanical and vaccume advance mechanisms along with the timing. Thinking more about it, definitely check your timing or just retard it some and see if it improves.
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

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