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© 2000 Brian F. Schreurs
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Sometimes you have to do strange things to diagnose a problem. Really strange things. For
example, one way to diagnose blockage in the exhaust system is to systematically remove each
obstruction. The first part is easy: disconnect the intermediate pipe from the catalytic converter.
If the car runs good, then the problem lies in the muffler area. If the problem persists, then it
might be the catalytic converter. 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.
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.
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.
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.
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.
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