2002 chevy-suburban 5.3 4wd p0300 Problem Need help

[swathdiver]

i am going to do a compression test as well do you know the specs for this car?

Don't remember but the specs have been posted on here before. Just make sure they are consistent between cylinders, within 10-15% I think.

 

[kamelred408]

ok so i unbolted the driver side cat. revd it up and NO MISFIRE!

it started to misfire at idle but i only unbolted the cat i could not lower it to much so i think it is to close and causing back pressure still..... CAR SOUNDS AMAZING with an exhaust leak lMFAO


So i should have trusted my scanner and just got a new driver side cat. here in CALI we have special ones so its not cheap

I will replace the cat and get back to you all


THANK YOU EVERY 1

 

[swathdiver]

ok so i unbolted the driver side cat. revd it up and NO MISFIRE!

it started to misfire at idle but i only unbolted the cat i could not lower it to much so i think it is to close and causing back pressure still..... CAR SOUNDS AMAZING with an exhaust leak lMFAO


So i should have trusted my scanner and just got a new driver side cat. here in CALI we have special ones so its not cheap

I will replace the cat and get back to you all


THANK YOU EVERY 1

Careful about buying those cheap Chicom cats, they barely last a year. I got mine from Magnaflow and they have CARB cats for you too. I went with a Y-pipe and replaced them both.

 

[Larryjb]

That cat failed for a reason. I've never had to replace a cat here in Vancouver where we had AirCare ( emissions testing) for decades. Your 02 should have lasted longer. It is possible the original problem was fixed.

I still have a gut feel about the intake manifold gaskets. If they are original, I'd replace them and check the knock sensors at the same time. (there is a tsb on the knock sensors).