Signs of clogged catalytic converters!?!?!?

Zero Signal said:

If they're clogged, the car would definitely bog down. It wouldn't miss like an ignition problem, just have no power and may sound strange. I've never heard of a cat 'clogging' though. My stock pre-cats went bad at 110k miles. The internal element actually became dislodged and was rattling around sideways inside the cat body which blocked the flow. Under normal driving you could barely tell. When I punched it, the car sounded funky like a WRX but went nowhere. I smashed both elements out of the precats with a crowbar which was a lot more fun than it should have been. No more problems after that and I still passed emissions.

Still, I'd do a tunup before dropping the H-pipe. You may need it anyway. Don't forget to clean the MAF. Do that first.

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HISSIN50 said:

A clogged exhaust is not nice to the motor. I've lost a cat before and the motor eventually shut down (out in the boonies on a trip, trying to make it back to civilization).

The best way to test is with a backpressure gauge. They're not common so if you choose you can:

Put a vac gauge on a manifold vac port. Start the car and hold the revs at 2500 or so. Note the vac gauge reading once it stabilizes. Keep it like this for 30 seconds or a minute and if the reading drops, that suggests you have an exhaust restriction. You might need to wait to do this until the car acts up if the blockage is mild.

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