Bad Cat?

2002 Yukon XL, 40k mi. -

I got a 'service engine soon' light the same day wifey comes home saying there is a "new rattle". The rattle sounds like a loose exhaust heat sheild, or even gravel caught above and vibrating on a heat sheild, but it resonates throughout the entire length of the exhaust system.

My best guesstimate is that it appears to be originating from inside the right (pass.) side catalytic converter. Had the local AutoZone read the code which said Cat Failure due to 1.) vacuum leak, or; 2.) engine oil leak into Cat, or; 3.) O2 sensor failure.

I tend to rule out 2 and 3 because of the loud rattle. Not sure if item 1 would even cause a rattle, so I'm leaning towards broken honeycomb inside the cat itself. Looks like the cats are integral to the 'Y-piping' from the manifold back to the single piping aft, therefore, I suspect a pricey fix?!

Any helpful comments or suggestions? Thanks

Anyone experience a failure/rattle from the emission system Smog Air Pump?

ACDELCO PT1116 [AIR PUMP] CONNECTOR,MOT-SECD AIR INJN PUMP OEM#12085212 $13.63

ACDELCO PT374 [AIR PUMP] CONNECTOR,SOL-SECD AIR INJN BYPASS VLV OEM#12102747 $16.20

The federal Clean Air Act requires that auto manufacturers provide an 8-year/80,000 mile warranty on catalytic converters. If yours is bad, the repair should be covered by the dealer. They will probably try to tell you the vehicle wasn't properly maintained, which is a loop hole in the warranty. Sometimes, however, the cats do just fall apart inside. If there's no visible damage to the outside of the cat you might have a shot of getting a new one for free.

Jim

Thanks, good to know because there is no damage to the cat housing or anything else undercarraige for that matter. Will know soon enough, taking it in today.

The good news - bad cat converter replaced under warranty. The bad news - during the cat replacement, the tech found: "Flex-fuel composition sensor falling apart, needs replacement, can cause massive fuel leak. $737.70 + tax." After 2 years and 41k mi. - out of service a total of 6 times and 4 weeks - I'm thru with this junk. Declined and looking to trade.

If you never plan to run anything other than trusty 87 dinosaur juice, I'd recommend yanking the sensor entirely. Good luck...

Take care,
Jerry

The good news - bad cat converter replaced under warranty. The bad news - during the cat replacement, the tech found: "Flex-fuel composition sensor falling apart, needs replacement, can cause massive fuel leak. $737.70 + tax." After 2 years and 41k mi. - out of service a total of 6 times and 4 weeks - I'm thru with this junk. Declined and looking to trade.

That's the 'ol "no warranty repair goes unpunished" strategy employed by most stealers 'round here. They'll be damned if you're going to leave their dealership without paying for something.

I'd say a $700 part that is "falling apart" after 2 years and 41k miles and that would cause a "massive fuel leak" is a pretty big liability for GM. I mean, how many disasters are averted by coincidentally finding the problem during a cat converter repair? How many others have burst into flames? I think it's BS - get a second opinion. Or remove it like Vroom says. Unless you run anything other than gasoline you don't need it.

Jim

GM optimized 'flex-fuel' engine systems for every blend of fuel up to 85 percent ethanol, and added a fuel composition sensor to detect what percentage of methanol is in the fuel and relay that information to the vehicle’s power-train control module...which adjusts the injectors and ignition accordingly. Since my fuel composition will most likely not change much, if at all, I wonder if removing the sensor altogether would cause any long-term harm or ineffecient operation?