If you have an IR thermometer, measuring temp before/after cats might show something. But if you have 4 O2 sensors, they should have already caught this if they are clogged.

And check to be sure someone has not cross connected the intake vac system with the cruise control "electric vac pump" system.

 

Hey savannah that

 

Hey savannah that's a good idea about the IR temp. I'll get the Thermal imging camera from the firehouse and check it. It has a thermomter in the camera. What temps would be wonky?

 

Don't know, but if clogged, you would think incoming heat about the same on both cats, but outgoing lower on one clogged. I'd look for difference between one side of engine and the other. Post a pix if you can. I know when I was looking for an exhaust leak with a $30 IR thermometer, the metal pipes read cold at start up, but the leak spot was 400F and rising.

 

I went ahead and put it on the lift today, I'll go ahead and wring off the exhaust pipe to manfold bolts and see what happens then. Before removing I'll shoot it with the thermal imager.

 

Thermal imaging camera test. After 5' at idle.
Driver side inlet temp at Cat... 231F outlet 187F Difference of 44 degrees
Passenger side inlet temp at cat 487F outlet 531F Again 44 degrees but inverted from driver side.
The camera is pretty neat. You can see the inside of the cat like the military movies look through walls. Driver side has about 3/4 to 1 inch diameter through the middle. Passenger side is more difuse across the entire converter.
Inference is that not being the same, one side has a problem. Lower temp driver side indicates clogged so exhaust not flowing. Or is the lack of flow result in less heat cause that side of the engine ain't running right.
Passenger side is flowing but outflow is higher than in flow. If clogged input should be higher by logic but how do you get increased heat at the outflow. Might be thinner pipe for better heat transfer.
So I think I'll just take a sawzall and cut out both converters. I'm not likely to replace the bad one and how can I diagnose further without a visual inspection. Could torch an inspection hole that could be welded back but its looks pretty simple to eliminate these as a possible issue.
Any thoughts?
Chief JD Robinson
Brasstown FD
Brasstown NC

 

My concern would be the difference in the input temps. 231 compared to 487 is mind boggling.

 

Danny yes there is a significant difference, but without a baseline reading to compare which one is outside the standard parameters. THe drivers side being that low sounds wonky. Exhaust temp is usually around 500 plus at the head

 

The average light off temperature at which the catalytic converter begins to function ranges from 400 to 600 degrees F. The normal operating temperature can range up to 1,200 to 1,600 degrees F.

More than a 200* temp difference between inlet and outlet(outlet being higher) indicates a rich condition.

 

Hey Chris, so I have a 44 degree difference. Not conclusive. But passenger side with higher outlet temp may be operating normally. So I should cut out driver side first, or just go ahead and cut em both out.