The way that I was told to check catalytic converter is to gettwo self tapping screw, runone into the exhaust pipe before the cat then remove. Do the same behind the cat with the other. Start engine and see the differance between the holes. Reinstall screws to seal it up with some RTV or just put a tack weld if you have a welding machine.A friend of mine told me that is how he checks them at his exhaust shop.

 

check the input temp vs the output temp... in higher than out = clogged, out = in = dead, out higher than in = working right.

use a temp sensing gun and have someone rev the motor to about 2k rpms while you do the test. this will ensure good flow to the cat for a better reading.

 

thanx guys i really appreciate the info. im gonna try that temp thing. i work in the hvac so i got one of those fluke thermometers.

 

just remember to have someone rev the motor to heat up the cat...

 

hey maybe ill give this test a try on mine after the checking the coil again

 

i get 11.75 MPG but im pushing it, over the red line and thats on a bad plenum gasket

 

do your cap and rotor if you didnt do it, mine was done before i bought it, and then i did it ,and the rotor was crisp, the metal plate was at a 90 degree angle, i was surprised it didnt misfire. but it ran better when i changed both

 

I've done a bunch of stuff to mine too, and Although my calculations show 15.8 highway, I still feel the truck can do better. Especially with this lag thing going on. From what I'm reading through, check your vacuum hoses. It appears, one way through another, wasted vacuum lessens your mpg. I doubt it's anything severe, but still worth a check in my opinion.

 

9 mpg is definitely not enough! I get 15 back and forth to work and the only thing extra I've done is all synthetic fluids. It got 14 or 14.5 before synthetics. Maybe it's my bed cover. Hope you find the problem.

 

Has he checked the plenum gasket?