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Discussion Starter #1
1st post!

After a few months the cats keep breaking up and start rattling. This is my third set. Unfortunately I did not keep the original h-pipe.

I'm fairly certain my fuel/air mixture is good, and I don't think I've been scraping over speed bumps.

Does anyone have these on their car with no issues?
 

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Qwik Enuff
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Do you still have your thermactor system (smog pump,tab/tad valves,tab/tad solenoids,vacuum hoses,crossover pipe on heads)in place and functioning properly?? If not,that could be your problem.That metal pipe,that runs from the tad valve to the hpipe/xpipe,is suppose to be attached to the converter fresh air inlet tube that's welded to the h/xpipe.This type of converter (with the air tube welded on)requires a fresh air source from the smog pump,otherwise the converter will clog,overheat and begin breaking up.This is the only thing I can think which might cause you to go through 3 pipes.The only other thing would be if the h/xpipe hangers are broken or the bracket(mounted to the bottom of transmission) that the h/xpipe hangers fit into is broken.I very seriously doubt there's an issue with the converters that would cause this to occur in 3 different pipes.If you aren't running smog,that's probably the cause.If you are running smog,you need to trouble shoot every component in the system to see if something is malfunctioning.If this sounds like what your problem may be,let me know and I'll post a detailed list for trouble shooting the smog system.

Newer catalytic converters do not use the Thermactor Air System (smog pump) because they are designed to work with an improved computer system that runs leaner and cleaner.(The cats on the hpipe you're using aren't the newer ones detailed in this description since they've got the fresh air inlet pipe for smog air + the absence of threaded holes for 2 additional o2 sensors)
They add an extra set of O2 sensors after the catalytic converters to monitor the oxygen and HC levels. Using this additional information, the improved computer system adjusts the air/fuel mixture for cleaner combustion and reduced emissions. If the computer cannot compensate for the added load of emissions due to wear and poor tune, the catalytic converters will eventually fail and clog. The periodic checks (smog inspections) are supposed to help owners keep track of problems and get them repaired. Use them on an 86-95 Mustang and you will slowly kill them with the pollutants that they are not designed to deal with.
 

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Discussion Starter #3
Wbrockstar thank you for your reply!

Ill have to check this weekend on the fresh air metal pipe. Though im guessing it's there, since a smog shop installed them for me.

Im not following on why a broken mount cause failure?

Thanks again!
 

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Wbrockstar thank you for your reply!

Ill have to check this weekend on the fresh air metal pipe. Though im guessing it's there, since a smog shop installed them for me.

Im not following on why a broken mount cause failure?

Thanks again!
Did you ever find out what was happening? I bought this exhaust end of 2015 and this happens to me too.
 
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