IMHO that is not enough to be concerned. Might want to go with your plan to remove O2 sensor... if an opening between engine and CAT doesn't raise vac, then maybe problem is somewhere else. If carb cleaner is being blown away from intake gasket test areas, might consider slipping off serpantine belt and making quick tests when engine cold. Then fan can't blow the carb cleaner fumes away.

 

I added some info I forgot in my previous post regarding the difference in inlet and outlet temps. From the data you posted, it seems that the driver's side is not up to temp yet and running a little lean, but the pax side is at temp and running a little rich. They should be roughly the same temp. You could also have some blockage in the pax side causing the temps to increase faster. Or the pax is fine and someone rodded out the driver's side because it was plugged up.

Remember, cats don't die, they are killed. Replacing a dead cat does not fix the original problem.

 

I think you may need to check your vacuum again.

To check intake vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle for most engines should be 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is 10 percent lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust.

Food for thought.

 

Hey savannah, I tried w/o the serpentine belt on no difference. O2 sensors will be easier to pull than cutting off the cats. I'll try that next

 

Pulled the O2 sensors. No change in vacuum, fuel pressure, or running. Idles at 10 inches of vacuum. Most I can get is 15. No joy at the exhaust pipe to manifold bolts. Wrung off 1 out of 3 1 more rounded off. Might just cut an acces on the side of the cats and gut em then MIG weld it back.

 

Thanks for the food, my thoughts were starving.

 

I'm eating cold pizza right now. I might share if your thoughts are still hungry...

 

Check vac gauge on another vehicle. But good to know if test equipment was "reasonable". 15 is a lot closer than 10....

 

The round one usually goes bad first.

 

Savannah, using 2 guages one I've had for years, the other brand spankin new.
Jafir, why 2 different designs? I'd figgured that one had been replaced in the past. Diagnostic wise re Chris Bob's post that some malfunction kills cats they don't just die, would it be one cylinder number 4 rear driver side had lower compression. Leaking intake would make that cylinder lean and not effect but leaking exhaust could allow rich to that side cat