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© 2000 Brian F. Schreurs
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The best way to test the catalytic converter for blockage is to punch it out -- you were gonna replace it anyway, right? We recently did just that to the Paradise Garage 1986 Chevy Camaro IROC-Z.

Here's our slightly battle-damaged catalytic converter, viewed from the passenger-side where it's easiest to reach.

The catalytic converter is conveniently located about midway down the length of the car. This means that neither lifting the front nor the back will provide enough ground clearance to do the job. If you have ramps, drive the front of the Camaro onto the ramps, then jack the back up and use jack stands. If you don't have ramps, use jack stands all the way around.

With both ends of the car lifted, it's easy to find the cat hiding approximately under the passenger seat. It's a big affair with a heat shield. It has (or had) an exhaust clamp on the front and a flange with two bolts on the back.

The two bolts had been replaced on ours, so we don't know what size they were supposed to be. Something around 11mm or 12mm probably. One of ours had to be cut off, and since there wasn't room for a Dremel, we had to do it with a hacksaw. Fun times for all! There are special blades available for cutting steel; these make the process a little less painful.

There's the driver-side flange mounting bolt, up there in the shadow where it's darn near impossible to reach.

The bolt on the other side, you'd better hope it's willing to come off, because even a hacksaw will have a hard time getting at this one. There's a special place in hell for whoever designed this flange; would it have been so hard to offset the flange so that it didn't have interference problems with the cat hanger and the heat shield? WOULD IT?!

GM. Sheesh.

Anyway. With the two bolts removed, the intermediate pipe pops right off. Unfortunately, with the muffler clamp on the front, the cat isn't going to pop off with it; it'll be stuck for sure. And since there's no way to visually inspect the cat with it still on the car, the only option is to presume that it's dead and must be replaced. But we're still going to gut the catalytic converter anyway so that we can be absolutely sure that was the cause of the restriction.

This job requires a big hammer and an big pry bar. Take the pry bar and jam it into the converter. Start banging around, tearing things up. Beat on it with a hammer from time to time.

Wanna see what you're doing? If you lay back by the left-rear tire, and shine a light into the cat, you can see the top 50% of the converter. Not that it'll do you much good, but it's kinda cool.

Probably while prying and poking, you'll think there are a bunch of metal baffles inside the converter. Well, the AIR tube crosses the middle of the cat, but otherwise it's nothing but cat material. It's not called a "brick" for nothing, y'know.

When you think you've got it all, or you get tired, stick a shop vac into the end of the cat to suck out some of the dust and bits. Then, fire the car up and let it idle for a couple minutes. This process blows out some of the chunks and loosens up bits of cracked brick.

Sweep up the brick dust (you don't want to lie in this stuff; in fact, you'd be well-advised to use a creeper, even after sweeping) and go at it some more. Repeat the shop vac and idle procedure.

The glorious moment: one catalytic converter having a difficult time digesting one three-foot prybar!

We did the full cycle three times before we actually had the cat completely gutted. Some of the chunks came apart just a little bit too large to fit through the end of the converter; for them, we got 'em wedged up against the outlet as best we could, then slid a GM distributor bolt wrench behind 'em and gave 'em a good punch in the arse. They all came out.

With the catalytic converter completely cleaned out, test the operation of the vehicle. If it runs much better now, congratulations! The catalytic converter was at fault. This was the situation with our car.

Replace the converter, or, if pressed for time, reassemble the exhaust with the gutted cat in place, temporarily. No harm will come to your engine from running without the converter. No codes will flash. Your car might smell a little stinkier, but that's about it.

These are the only solid chunks we got. The rest was mostly dust.

We replaced the two flange bolts with 11mm on the driver side and 3/8" on the passenger side. Note that getting a nut onto the end of the bolt, on the driver side, is nearly impossible (burn, baby, burn). If you have a magnetic holding tool, hold the nut with that. If you don't have one of those things, get one -- we dunno how you'll do this job without it.

And that's really about it! No problem!

We're so relieved to have our exhaust system working properly again. It runs better and sounds better. This diagnostic procedure really worked for us, and it should work just fine on your car too. And, saving some money on this job is a huge plus! Sometimes the simple stuff works best.