yield2s

after a aggressive run through malibu canyon i noticed a rattling noise coming from the cat. it sound like obx header resonance but 10x's louded and at almost all rpms during speed increase and decrease.Ive checked all external bolts and shields on exhaust but no fix.
Here's the big piece to the puzzle,ive ran about 3/4 of a tank of fuel mixed with greased lightning fuel inj. cleaner as recommended by my service manager to solve a sticky trottle body and rough idle problem,It solved that but i think the extra heat from the cleaner burnt up my cat.
WHAT DOES A BURNT CAT SOUND LIKE?

asiankidd

depends on the situation, but a burnt cat from using a fuel additive should not have caused that, its possible that the cat could have shattered causing it to rattle or a heat shield must have gotten damage and starting to hit or rub against the cat, take a visual inspection if you can, and it its ok take out the cat and look at it, worse case you need a new cat

good luck

JON

yield2s

well its sitting at the dealer now, hopefully they replace it.

yield2s

"could not reproduce" go figure.
well when i picked it up it didnt do it,so i start driving home and sure enough about 3 blocks it started rattling again(sounds like all the heat shields under the car are loose,but they're not!)
but check it out i fix it. i noticed it did it after a few minutes of spirited driving. but then stopped when i was just crusing and when i was waiting at a light so i realized it was deff heat related in the catalitic converter.
well to cut it short for all, i was running fuel injector cleaner in that tank of gas which was super heating the cat causing the inners to expand beyond normal and vibrate against shell. I put another 12 gal of gas in and drove 50 miles and no noise at all.