1987 Coupe - To Cat or not to Cat (and how)

Willybill32 said:

I'm curious. The smog pump on my '86 5.0 seized years ago, and it was abandoned. The car still has the stock H-pipe and cats, and I can't tell of any problem. How do I know the cats have failed?

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They gum up internall due to unburned fuel not burning off

Engine tune plays a big part. The o2 is injected to increase the efficiency of the cats and burn off that unburned fuel mixture. They need to be hot for this to work, so the o2 injection helps with this.

Ththe reason modern cars don’t use air pumps is actually two reasons. #1, cat design is more efficient, and #2 is the engines burn cleaner and without excess fuel.

So eliminating the air pump isn’t an instant death sentence of your air/fuel mixture is not overly rich.