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Got a 4.3 in a GMC 4x4 that fouled a plug and was blowing cold exhaust on that side. Also a tappit sounding loud on that side. Replaced all plugs. Still missing. Could someone tell me what could be the problem?

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75 Luv 350/TH350 (Project in progress)

If the tappit sound is in your top end, I'd say you maybe got something wrong in your lifters or valves. It could possibly be a bad lifter or a burnt valve, or a bent pushrod, or all of those. Only one way to find out for sure - pull the head and have a look. Have you done a compression check on that side yet? A wet v.s. dry test comparison will tell you if it's rings or valves.

Sounds to me like it's time to RTFM and investigate it, that's for sure.

Taz is right I was with my wife and mother in law on our way to redding and it started doing the same thing you are describing but really bad up hill she would even put it down two third and have the thing flored barley doing fiffty and it would make that ticking noise it's didn't help that we were towing a trailer with four quads but we went to my mother in laws dads house who happens to be a bit of a mechanic and he diagnosed the same problem. Also it is a 99 chevy suburban. Hope that helps

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Thanks Tazman for the diagnosis. Sounds like I need to do a compression test on that side. If compression is OK then I will pull the head off and see whats going on. If compression is off on that one cylinder that fouled, then I guess it would be the rings causing the problem?

What do you mean by a wet v.s. dry test comparison?

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75 Luv 350/TH350 (Project in progress)

Sounds like the same problem, broddyman23. My son hauled his & cousins bikes up onto the mountain when it happened. It was running great the day before. Sudden death...

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75 Luv 350/TH350 (Project in progress)