Four-point-Two said:
Belt is on correctly. Could a compression test gauge be used with an adapter fitting for the O2 sensor thread size? Not sure where I could get one, guess I could buy or rent one?
Yeah, I don't know how a person could get the belt on incorrectly.
Here's what I've learned by research on this site and the general interwebs -- I also replaced my thermostat and wondered about cat health, but I haven't gotten around to doing the testing since my mileage is good, there are no codes, and everything seems to be running well.
There are two O2 sensors, one on the exhaust manifold, and one on the back end of the cat. It appears that if the cat is blocked it can cause serious engine performance problems. The quick way to test it is to take off the O2 sensor on the exhaust manifold (using a special socket that is like a spark-plug socket with a slot up the side to accommodate the wiring that goes from the sensor back to the PCM). Install a pressure gauge, fire up the engine, have a helper rev it around, and see what it reads.
A backpressure gauge is available for sale on the internet and in-store. It doesn't take much pressure to indicate a cat problem, so in addition to the fitting the gauge has to have the proper low-end range on the scale.
I've read that if you are not satisfied with the results of just the manifold reading, you can also re-install the manifold O2 sensor and take out the down-line sensor behind the cat, and compare the readings. In that case, a significant difference would indicate a blocked cat.
Once I finish my front-end rebuild, get new tires, replace my windshield (not necessarily in that order), swap in a G80 differential ... I might even get around to doing this test myself.
Tons of youtube vids on this test. Gauge can be had for purchase from 40 to 100 bucks. Maybe you can rent/borrow at AAP, don't know.
