2002 3.8L V6 -

A little backround first. A few months ago, out of nowhere my car started losing power. Over the course of two or more weeks, it got so bad that I couldn't go over 45 mph. I determined that one of my spark plug wires was bad, so I changed all of them and the car started driving great. Also around the same time I got a P0410 code - Secondary Air pump malfuntion. I ignored it because from what I read it doesn't cause drivabliltiy issues. I've been driving the car ever since, and the problem is starting to happen all over again, and if I'm on the expressway going about 50 or 60mph and I give the car more throttle the, there's a clanging noise coming from the engine - like bap bap bap bap, in rapid succession. The rpm's shoot up and the car doesn't go any faster. The plug wires appear to be fine. ANy ideas what's causing this?

Possible bad CAT converter. See advisory at link below.

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

Also, what is the current mileage?

I think you may be right. That would explain the clanging noise, and plus when I'm going up a steep hill, I loose alot of power. It must be the fragments rolling to back of the cat blocking the pipe.

Just an educated guess. How many miles do you have for possible warranty purposes?

I had the same problem with my wifes 1999 GP a few years ago. At the same speeds but mostly from getting on the freeway from an on-ramp or trying to accelerate from 50-60 mph.

Turned out to be a valve in the transmission. I don't know which valve but perhaps the pros would have a better idea. It seems to be common. I know of another GP owner who had the same issue.

Cost at the dealer..if I remember correctly was in the $400 range.

Based on the OP's symptoms I would pursue the CAT converter avenue before looking into a possible autotransaxle issue that may not exist and due to the strict warranty limitations to get the work covered for free at the GM dealership. The major difference with any 2001-2002 models with SII 3800 engine versus the 1999 is the advisory issued by GM admitting to an issue with the CAT converter. As a matter of standard policy when a member posts a possible CAT issue with any 2001-2002 we always refer them to the advisory and recommend that course of action first.

GM's standard CAT warranty is 8 years or 80K miles, whichever comes first. For relevant 2001-2002 models the warranty was extended to 10 years or 120K miles, whichever comes first.

Just had the exact thing happen to my 99 gtp. It was a clogged cat converter.

Thank you so muich. I took it to the dealer and they confirmed that it was the Cat Converter. They replaced it free of charge and even gave me a ride to work while it was being fixed. Thanks again!