Just curious but how can you check for a clogged converter?

 

If your catalytic converter is clogged, your car will not accelarate beyond 15-20 mph. Trust me, my other '84 Z had a plugged cat, and at WOT it would only do 15 mph (and sounded overloaded). Also look at the exhaust (have a friend rev it) and see if the pressure increases (alot). If it just oozes out while rev'ing it, then your cat is plugged.

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George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCCA, SCFB, SC3GFB

 

Quite often, they plug up gradually so you don't notice the lack of performance. One sure-fire way to find out is to find somebody with an infared thermometer that is capable of very high temps. If the cat is excessively hot, it's likely plugged. I don't remember the temps though. I think 1600+ indicates that it's plugging up.

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"I didn't know a bored out Ford could go so slow" -Shenandoah

 

Two ways I know of to check for a restricted exhaust...

One is to pull the O2 sensor, and check the back pressure...a 0-15 PSI gauge (like the ones for fuel pressure) work well enough...at 3000 RPMs, and decent exhaust shouldn't have much more than 1-2PSI backpressure...anymore, indicates the exhaust is restricted. I think GM says in my Helms, spec is 3PSI...but my '89 with the stock cat, muffler and exhaust has about 1.25-1-5psi.

The other is to hook a vacuum gauge up to the intake, note the intake vacuum idle reading, accelerate the motor to 3000 RPMs and see if the vacuum is within an in/hg or so of the initial reading...any lower indicates a restricted exhaust. i/e you read 19in/hg at idle, and only 14 or 15 in/hg at 3000 RPMs, your exhaust is restricted.

Both tests done in neutral/park...not driving the car.

 

Any muffler shop should be able to test you exhaust for backpressure and tell you if it's clogged or not.

Mine plugged up gradually and I started noticing a drop in performance almost like the car was being choked for air. We took the exhaust loose from the back of the converter and I drove it down the road...I had almost no increase in noise and it didn't help any for my performance, so I then realized I had a plugged cat or partially anyways. Yo may be able to see inside it once you remove the exhaust but it depends on which end all the crap decides to braek apart at. Mine broke apart on the engine side so the cat looked normal from the muffler side.

If it is plugged by a high-flow cat to replace yours with, especially if you have headers and a cat-back system. If you still have the stock exhaust manifolds and muffler it won't hurt to remove the old cat for a straight pipe.

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1988 TA 300+hp 350 w/ TBI and Holley TB unit, Holley projection intake,
WC T-5, 3.42 gears w/ Auburn posi. MSD 6A, edelbrock TES headers, dynomax 3" cat and cat-back system, ACCEL coil, polyurethane bushings all around, aluminum driveshaft, Mr. Gasket open air cleaner.

1993 S-10 w/ 4.3L V6 TBI, slightly bigger cam, Mild polish job and 3 angle valve job on heads, Edlebrock TES headers, Dynomax cat back, MSD 6A, ADS chip

2000 Kawasaki KX 125

 

Thanks for the ideas, guys. I don't think I've got a problem with mine now but I've noticed various postings where someone had mentioned finding a 'clogged cat' and I had wondered how they managed to arrive to that conclusion short of pulling the cat and just inspecting it....