P0101 and P0300 codes Runs really bad
 

Hi this is my first post on this forum. I have a problem with my 2004 Suburban I hope someone can help with. It runs really bad, no power, clatters and backfires will hardly go over 45. CEL is on and sometime flashing. Autozone read codes P0101 - Mass Air Flow (MAF) Circuit Range/Performance Problem
P0300 - Random misfire

Changed MAF with my Corvette. Corvette still runs fine (no codes). Suburban still runs bad. Checked cats temp front (300 degrees) , back (500 degrees). Checked fuel pressure at 45psi . Where do I go from here? What do y'all think is going on? Thanks for any help and advice.

If anyone is interested. This turned out to be catalytic converters. Confirmed by removing before cat O2 sensors and taking for a ride. With sensors out it ran good and very loud. Replaced cats. Runs like new again.

Thanks for follow up on your post and what the fix was! its what makes forums work :)
FWIW, my 07 Tahoe, when I check the catalytic converters temps they are more around 1100°-1200° under normal driving conditions...

Cat
 

I also had the P101 and P300. I cleaned the mass air flow sensor and it did nothing. I took out the K&N air filter that was in therefor 12 years and put stock back it just to rule K&N out, still did nothing. Shelled out 100 for new MAF, nothing. I hooked up a pressure gauge upstream of the cat with an adapter that screws into the o2 sensor port and found restriction on the driver side. Bought a new cat online for 130 took it to a shop, the guy says P101, P300, its not the CAT but if you want to pay us and keep throwing money at parts, we will put it in. 5 minutes later, shop guy comes in and says the CAT was 95% blocked. Replaced the Cat runs great no codes.

Brian: Welcome to the forum. Thanks for the info.

Same problem
 

My 2003 Silverado 4.3 was loud and was told to change manifold gasket which I did and now I have codes 0101 and 0300 . Truck is quite now and when idle sounds okay but as soon as try to take off it’s barely moving and will have small backfire sounds . I was going to change 02 sensor but now I’m thinking it’s probably the cat . Is there anyway to tell without removing and driving without 02 sensor ??