2002 Chevrolet Avalanche Rattle noise and P0171, P0174

2002 CHEVROLET AVALANCHE

175,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC

CROBERTS

MEMBER
6 POSTS

I changed the valve cover gasket, exhaust manifold gasket and flange ring on the drivers side. The PCM was showing that it wasn't reset yet, yellow LED on tester, for about 2wks. Driving at night and the CEL came on with codes P0171 and P0174. I also noticed a rattling/dinging sound coming from the driver side underneath. I went underneath and sound is coming from Cat area. Is this a sign that the cat is bad/going bad cause of a lengthy O2 sensor repair needed (about 5mos+). I always knew that there was a sulfur like smell on older models when cat was bad or glowing red cause of blockage. Also if this is bad is there a easier cheaper CAT to be replaced then the $700 OEM "Y" assembly?

Jul 31, 2014 at 2:24 PM

WRENCHTECH

✓ASE Certified Mechanic
20,761 POSTS

Man,you are wrong in so many different ways.

Where do I start?

You have a lean condition so I don't know why you are messing with exhaust.

Your car is not glowing because it is blocked. It's glowing because the engine is misfiring so bad that the cat is getting filled with raw fuel and overheating. If you continue to do that, you will end up needing a cat because it will melt the substrate. If the Cat is rattling, it ,may have already happened. If so, check with an exhaust specialty shop to see if an aftermarket is available.

Concentrate on finding your lean problem. Check thoroughly for any vacuum leaks or leaks in the intake snorkel first. You may need a smoke test to find the leaks.

Jul 31, 2014 at 3:18 PM

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