1983 Delta 88 307ci

Hey Guys, I just replaced my catalytic converter. After installing it, I immediately notice a difference in the exhaust smell. Beforehand I was running straight unadulterated exhaust, the old cat was hollowed out. (EPA alarms just went off) Anyway it smelled like the exhaust of an older, pre-cat converter car. It almost seemed a little rich in my opinion. But over the last few years i've changed the O2 sensor, canister purge valve, throttle positioning sensor, etc. I've even checked the dwell on the mixture solenoid at different times and slightly adjusted mixture screws accordingly. The engine always ran well but the exhaust at idle always smelled slightly rich no matter what I did.
From what I've read, a new catalytic converter can run extra hot if the exhaust is too rich. And in a matter of a couple of hundred miles, end up burning itself out and become ineffective. Or it could get clogged and create too much back pressure. My question is what can I do to make sure this won't happen? I was going to hook up the dwell meter to the carb again to make sure the dwell on the mixture solenoid was floating around 30 degrees, but is there anything else to check as a precaution?

Thanks for the help,
Rob

 

Rob, since you installed a new catalytic converter you need to ensure that your car is properly tuned to factory specs. Have you done any upgrades to the engine (ie. cam, intake manifold, headers)? If so, I wouldn't run any catalytic converter on the engine. As you said, if a car is running rich the catalytic converter can get hot and the catalyst inside the converter can be damaged. From my understanding, this was a common problem with older catalytic conversters used in the late 70s that had the removable pellets. IF you have a newer aftermarket catalytic converter you should be fine as long as your settings are where they are supposed to be.

 

You are correct about an overly-rich mixture causing the cat to overheat and melt down. You must make sure that the CCC system is properly adjusted per the CSM. You must also be sure that the A.I.R. system is working properly, as the main function of the A.I.R. pump once the system goes into closed loop operation is to blow additional air into the cat to prevent meltdown.

 

You also need to watch out for cheap cat's, a lot of the inexpensive one's will burn out every year whether tuned right or not (ask me how I know).

 

So Joe, if my AIR pump stopped working about two years ago, what will eventually happen to my cat? Will the inside literally melt and clog up?

 

That is a good question. I am assuming that if your car has a cat with the provision for the air pump, it needs to be operational to keep the cat functioning properly. I remember quite a few cars from the 70's that had cats but no air pump and they were fine.

 

Agreed.

 

Thanks for all the responses. Everything on the engine is stock. I believe the car is properly tuned, I've gone over many of sensors and don't have a check engine light. It also seems to run pretty well. As far as the A.I.R. system, everything is hooked up and in working order.

The brand of the converter is Walker, it was around $140. There were other cheaper options but they were names I've never heard of. There weren't any other more expensive options, except for a California compliant one. But I just wanted a stock replacement since the car has been in New Jersey it's whole life and doesn't have to pass California emission standards.
I rechecked the carb mixture solenoid with my dwell meter, cleaned the air filter (K&N), and changed the oil. Then I took it to the inspection station and it passed! So the cat seems to be doing it's job at least for now, hopefully it stays that way.

 

I agree with Joe, the AIR pump pushes more air into the cat and without it would become hotter than it should. I guess in an extreme case it could eventually melt and clog up or just become less and less efficient over time and not control emissions as well.