I just had my clogged cats replaced with really high flowing ones

After the work was done, the car ran and sounded great. I parked it for an 1-1/2 and restarted it and it now has a really loopy idle and stumbles everytime I stop at a light. There's also a strong smell of gas (running rich I assume). I'm going down to hook up my scanner now but I just want some feedback in the meantime.

It's hard to think straight when youhave to be at a wedding in NC tomorrow night.

Thanks all.

Scott

 

Did you keep your AIR fitting...If you didn't replace it with a cat that has an AIR hookup then the car might be running rich.

 

Yes, the fitting is still there but it's doing nothing because the cats have a straight pipe through them. It just looks stock now.
What could make it run that rich?

 

How old is your O2 sensor. Might be a good place to start.

Also, unhook your battery for about 15 mins and hook it up again. That will reset the ECM.

 

The O2 sensor appears to be functioning when viewed with a scanner and it is old but why would this happen right after putting straight pipes on?

I also disconnected the battery for a half hour with no change. Should I have done that right after the exhaust work?

Could it be that the ECM had somewhat adjusted itself to the bad cats and freeing them up screwed everything up?


I'm definitely at a loss.

What are some causes of running rich?

 

Well I think the most common cause of running rich would be a bad O2 sensor. I guess a bad fuel perssure regualtor could also do it.

I don't know why it would happen right after putting on the new cats. It is a possibility that the two are not related.

 

If the exhaust system has lost good electrical grounding as a result of the work, the O² sensor signal may be low, and the result would be a rich mixture.

Also, with dummy cats installed, the exhaust will smell a lot different (like exhaust USED to smell) and you may think you're rich as a result.