Ok Back story on 2008 Chevy Suburban1500 LS 5.3 with AFM Flex Fuel , We have had the vehicle for 3 years not got it with 130k miles on it now has 148 k miles on it . We fought the usual oil consumption issues in the past have put new plugs , wires , coils , brakes , pads etc. anyways you get the gist I've tried to get the maintenance back in order. Driving home the other day filled up with gas and drove probably another 5 miles and came to a red light when accelerated from the light it was like the engine ( which was running fine before the fuel fillip and after until this point )just wouldn't accelerate over 25-35 MPH massive decrease of power so stopped opened up the hood ( at this point still hadn't thrown a code when I attached the code reader it still showed no active codes ) noticed where the exhaust manifold studs ( driver Side ) mate up to the exhaust that flows into the Cats was bright cherry red . I assumed the cats were plugged so I banged on the cats to clear the blockage. was able to clear enough blockage to limp it home another 5 miles . So all caught up to today , replaced the entire cat exhaust from the manifold to the meet up for the muffler , replaced all 4 o2 sensors . Then started it up and it threw P0171 ( system to lean bank 1 ) and P0300 ( random misfire ) codes , checked all the new o2 sensors they all seem to within ranges of normal use. so next step I replaced the exhaust manifold figured since it was cherry red it probably warped and took it off it appeared to be slightly warped but not to bad. hoped that would fix the issue and nope , so next step I have bought new exhaust gasket and fuel injectors ( since they will be off anyways ) my worry is if this doesn't fix it what else could be causing the issue ?

I will attach links to a Google Drive Document that show s the codes and some of the data... Im just a at home garage mechanic so my knowledge only goes so far so so any help would be appreciated

https://drive.google.com/file/d/1_75...ew?usp=sharing

https://drive.google.com/file/d/1Q5i...ew?usp=sharing

 

Did you use Genuine GM O2 sensors. Aftermarket sensors cannot be trusted, too many issues with them, even new out of the box, and that makes for confusing diagnosis after using them. Any sensor replacement. factory ones should be used.

 

no I did not I used TRQ sensors from 1a auto could this possibly be the issue ?

 

As a follow up, there are a lot of aftermarket parts out there that just didn't have the quality control they should have had like imported junk.

There are a lot of good domestic manufacturers that offer quality aftermarket parts. The object is to watch where they came from.

OEM parts rarely give any problems because dealerships can't afford comebacks due to poor quality parts. You might pay a little more, but do the job once.

You might look for a vacuum leak on the bank producing the code. Maybe there was a series of injector problems, but since you are replacing them, best to see what you get when done.

 

So to Close out this thread finally gave up checking what i knew how to fix and sent it to the shop , turns out it was a bad ground which caused the cascade of issues.

 

Thanks for reporting back. Did they elaborate on which ground it was?