I have an AP1 MY 2001 49,000 miles with no mods. I've had a bad rattle/knocking sound at lower RPM and under load for the last couple months. The sound is not very rhythmic like you would expect from a rod. Got a P0138 CEL yesterday. Rapped on the cat with a rubber mallet and could reproduce the sound.

My diagnosis is a Bad catalytic converter that has wasted the O2 sensor. Does anyone disagree?

If you agree which cat and O2 sensor would you buy? I really don't want to fork out the money on OEM parts if I don't have to, but will if it's needed.

Is this a DIY job or do I seek professional help? I have the tools and I'm mechanically inclined.

Thanks Ron in Tampa

 

Buy a BERK HFC, and a Denso o2 senser done!..... HCF= 249.00 plus shipping.
Denso rear o2 senor OE style $42.79 plus shipping

it sure beats the heck outa of the stealership!! BTW I'm not selling these parts just giving you an idea of how much they cost

As far as doing it yourself....if you can get the CAT loose then do it. Thats the only hardest part since the CAT tends to get stuck and wont come off!!

 

Take a hammer and some pipe to the inside of your cat and hallow that puppy out. Takes about 30 minutes. Makes stock exhaust sound a bit more aggressive, gives you a little bit more power. This is a free fix. Any other will cost AT LEAST 100 dollars. You'll need to buy 2 spark plug non foulers that your o2 sensor will fit in. Screw them together then screw one end into your hallowed out cat, and put the o2 in the other. This will keep you from throwing a CEL.

 

i agree hollowing out the cat makes for awesome sound but goddamn is it a pain in the ass. i cut mine in half and drilled a billion holes then hammered, pulled,pushed ,beat,pryed and finally got it all out BTW it was well worth it and no cel with 2 defoulers

 

What ever you decide to buy I'd put on myself if I were you. TONS of PB Blaster on the bolts and nuts... let it soak for a few hours or even over night and reapply as much as you can while soaking. They'll come off

 

UPDATE: Replaced the cat and the O2 sensor. The old cat was shot. The core had completely come loose and sheared the O2 sensor off. This, after reading is a common problem. Replaced the cat with a Berk HFC and used a Denso direct fit, OEM style, O2 sensor. I used all new gaskets springs and fasteners. Out the door cost including shipping was about $330. Soaked the bolts with PB Blaster and Liquid Wrench several times over the week waiting for parts. Every bolt came off with almost no effort. The easiest job I've ever tackled. Total time less than 1 hour working slowly. The best thing is. The car sounds totally different now, much quieter. I've had the car for about a year and always have had rattles and rumbles. Lately the knocking. I thought I had the," clutch buzz" people talk about on the forum. No more buzzing, rattling, rumbling or knocking. I wish I had done the job months ago.