Thread: Temperature readings pre/post cat - normal or problem?

Originally Posted by Fivefingerdeathpunch

Temps seem normal to me.

OK. As I keep reading about it, the old rule of thumb that says there should be about 100 degrees difference between front and back is just that, "old."

From http://www.aa1car.com/library/converter.htm

"In many late-model engines with multipoint fuel injection, combustion is so clean that the converter has little to do and the difference between the inlet and outlet temperature may only be 30 degrees F at 2,500 rpm - which is a lot less than the old rule of thumb that says a good converter should show at least a 100 degree F difference fore and aft at cruise. At idle, the converter in many late-model vehicles may cool off so much that there's almost no measurable difference in fore and aft temperatures. So checking exhaust temperatures fore and aft of the converter at idle and 2,500 rpm is NOT an accurate way to determine if the converter is working properly or not."