Ron U.S.M.C.

Should I reset the ECM after a CAT change. (disconnect the negative battery cable for 5 minutes.)
And what would be the re lean cycle ? How should I drive the car ?
I have a SMOG test in 7 days.

paulo57509

I wouldn't bother doing anything. It depends on what state of tune your engine is in but a new converter should bring the measured numbers down to almost nothing.

IMO, you need to make sure you're engine isn't slowly poisoning the new converter or you're going to be replacing it again in a few years.

When I replaced the converter on my old Acura Legend I drove it over to the inspection station immediately after I bolted it on (2.1 miles). No freeway driving, no tank additives, no tune up, no oil change....nothing.

Before:


After:


This is a stock engine with 437,835 miles on it. Yes, it's most likely poisoning the converter with blow by. The before converter is only 5 years old with 40k miles on it and it's already getting weak.

BTW, who the heck drives a car at a constant 15MPH??? Bogus test IMO.

Good luck and post up your before and after numbers when you get your certificate.

Ron U.S.M.C.

Thanks for the reply.
The car went through a really rough time not long ago.
I believe that's what did the CAT in. It was a 9 year old Magnaflow.
The tune now is like night and day.The adjustments I have made now that the problem has been fixed is allowing it to run as I believe it should. Timing is dead on and min. Idle speed is also dead on so as long as the Thermac Switch is not causing a vacuum leak its all set taking that air flow into consideration.
Hopefully it's enough.