Power loss and noise over 5000rpms
 

So the car's at the Mazda dealership right now for one of the airbag recalls, and I had them check compression on the engine while it was in there. Lately I've been experiencing power loss and the engine almost sounds like it's choking, above 5000rpms. This usually occurs when the engine is very warm, driving around 20 minutes or more. No CEL at all.

The Mazda mechanic told me that one chamber in one of the rotors has slightly low compression. I will get the exact numbers from him when I pick the car. But he also said the cat was clogged, which was my first thought when this all started happening.

I'm running with BHR coils installed within the past 2 years and newer plugs. I also have a BHR midpipe and ceramic catalyst, also installed around 2 years ago. The mechanic is telling me that the cat is clogged because of the low compression issue and just replacing the cat is pointless.

I agree with this in that I wouldn't install a new cat on an unhealthy engine; however, my question is whether the symptoms are directly due to that one slightly low compression reading, or from the clogged catalyst itself.

I was considering deleting the cat temporarily to test this, but wanted to get some input from the group. Obviously I'll be looking at a new engine or rebuild sometime in the near future. But when my first engine had compression loss, I had only a hot-start issue and never experienced the engine choking at higher rpms.

As always, any input or suggestions would be greatly appreciated.

A bad cat will clog the exhaust and cause bogging. I had the same problem with a dying engine and clogged cat. I gutted it and it ran well until the engine finally died.