My car had the P0420 engine code so I gutting the cat's and put O2 spacers on the 2 O2 sensors behind the cats... within 50 miles of that my alternator went out and I replaced that. Now my car keeps on pulling the P0455 code. I have not replaced my gas cap, but have removed it and put it back on to make sure it has a proper seal... the car still pulls the code after about 75 miles of clearing it.

Could it be because of my gutted cats, or did something else happen that I'm not aware of? If so, what should I look for to troubleshoot?

 

I did a smoke test on it today, no leaks found. The only catch is that I had a full tank... we'll see if the light comes on when I get below half a tank.

 

Something to do with the EVAP system, so its unlikely you gutting the precats or replacing the alternator had anything to do with this problem.

 

I didn't figure it did, I was more thinking if there's an evap pipe around that area that I worked that could have been knicked or something in the process of pulling things out.

 

Unless you pulled the whole exhaust system, you might of hit something by the mufflers, that's where some of the EVAP system sits.

 

check your vacuum line connections under the hood. If you gutted the rear pre-cat by pulling it off the car, you had to pull the intake manifold to get to the two bolts for the pre-cat and might have forgotten to re install them.

 

ran the smoke test again with the tank empty, smoke came out the charcoal canister in front of the fuel tank... is there a valve on it that I can replace or will I need to replace the entire unit?

 

There is a valve right on the canister that relieves pressure that sometimes gets stuck open its pretty symple to replace I think all it is 2 10mm a plug and one hose try that and check back

 

Replacing that valve should fix the problem

 

ya, I replaced the valve... was cake... problem solved... now I have a P1166 code coming up. I know they are not related. Does anyone know which O2 is erroring?