2001 Grand Prix catalytic converter

I have a 2001 Grand Pix 3.1 aprox. 150,000 miles. About 5,000 miles ago had the fuel pressure regulator go bad. I replaced it and all was well until had a code p300 (random/multiple misfire). I changed plugs and wires at this time. The car now seems to lose power above 3000rpm while driving.

Now I am getting a p420 code. I checked engine vacuum which is 16 at idle, which if adjusted for altitude would be 21 at sea level. Which I think is with in limits. When I open up the throttle vacuum goes down than comes back up to 16. I can't get it to rev pass 3000 while in park probably because of the rev limiter.

Do you think previous problems caused the cat to go bad? If that is the case can you tell me if the Magnaflow or Walker would be a better replacement. I am talking about the direct fit models.

I have not taken the exhaust down pipe off before the cat. If I have to take this off I might as well just change the whole unit.

99% of the time the P0420 DTC means a bad CAT converter. Get it replaced instead of wasting time. A hi-flow Magnaflow is fine and relatively inexpensive.

The random misfire either caused the converter to go bad or you had defective one from the start if it is the original. See link and advisory.

Click here (http://www.automotiveforums.com/vbulletin/showthread.php?t=681283)


Note: Advisory is applicable to GPs with the 3100 V6 and GM did replace many for free but you are out of the window now.

I purchased the car new in Oct. 2000 and it has the orginal converter. I guess I'm out of luck on the warranty claim because of mileage. I'll order a new cat and install. Thanks for the help.

What was your FPR doing when it failed? Ruptured diaphram, allowing raw fuel to be comsumed through the vaccum line? If so, I'd suspect an overly rich condition burnt out your converter.