ok so let me start this off by saying i have a 2000 blazer ls 5 speed 4.3l and yes its straight piped. i had to do this as it was a cheap fix for a clogged cat at the time. since then i have heard this popping almost like a back fire from this can i put on it. my CEL is lit up and im not too worried about it but my question is...is it popping because of the lack of back pressure? or could it be burning up valves? im going to stick a high flow cat with the super 44 flowmaster on it soon but i dont want this problem to continue into that. i lost alot of torque since cutting the cat off also. power has went down but its still fast. and will the o2 sensor work properly with a high flow cat? if not ill just put a simulater on it. opinions anyone?!?

 

"can"? Could you describe that?...

 

can is in 3a racing muffler that i got from auto zone. its a cheapy and i personally classify it as an oversized resonator. you can see right through it if you look down the pipe. i need my torque back.

 

Stock manifolds and y-pipe?

 

yea everything is stock till it gets to that can which is located right where the cat used to be. there is no piping after the can. it just stops. like i said cheapy fix. i didnt have alot of cash and was putting in a new clutch at the same time which is where all the money went. at some point im going to be switching to headers which summit sells for a decent price. something to clear it up a bit but i heard a sound clip of the flowmaster 44's on a blazer and it sounded nice. this is too loud and raspy.

 

Have you had the codes read? Did you ever figure out what had caused the catalytic converter to melt down initially? I am wondering if you don't have a rich condition that is allowing unburnt fuel to ignite in the exhaust.

 

code is popped up from the o2 sensor being zip tied to my frame so i dont have to spend the 91$ for a new 1. and i think it was from when i first for the truck there was some hesitation so i put fuel injecter cleaner in it and hopped it up on a tank of 93 octane. finally figured out that hesitation problem was caused by an oil charged k&n air filter in the air box gumming up my maf sensor. the cat went shortly after i fixed that problem. it doesnt pop constantly just when im barely on the gas at cruising speeds. if i let off or mash on the gas it doesnt pop. i had a wierd idea that it might be the wind making it pop cause its sporatic. tis why im asking cause i dont wanna think its something when its nothing or vice versa.

 

The reason you are having a problem is because you don't have a complete exhaust system.

Without the cat and with the O2 sensor ziptied to the frame your engine is receiving conflicting readings from its sensors about your exhaust composition which helps to determine your air fuel mixture. Add to that the lack of back pressure due to missing 3/4 of your exhaust system and your bound to have some issues.
I imagine your gas mileage has gone down the tubes a bit as well.

You can run without a cat on your truck (illegal as it may be) but you still need your full exhaust as well as having that O2 sensor installed in the straight pipe.

Your better bet to run the exhaust without the cat would have been to cut off the old cat and install a temporary straight pipe to bridge the gap. You can get an O2 sensor mount for a straight pipe at most auto parts stores for around $5

Remember running without a cat is illegal on any vehicle 1995 and newer almost everywhere.