I have a 2008 Chevy Silverado Flex Fuel with 208,000 miles on it. I am having an issue that I believe is due to a clogged catalytic converter. I keep getting sporadic lean codes (p0420), the gas mileage has slowly degraded from around 16.5mpg down to 12mpg. At cold start, truck is tough to start (starts but sputters), but once warm it is fine. Also, cooling fans fire up immediately upon starting truck. I even get a rattling noise from under the truck. I am going to replace the cats, but they are expensive and I was wondering if I can buy universal cats which are much cheaper and have someone cut and weld them in. I am asking since this is a Flex Fuel vehicle and want to make sure that there isn’t anything special about the cats and functioning of the O2 sensors that a universal cat could foul up. Thanks.
P0420 is not a lean code.
Unfortunately mixture problems and degrading cats are a known problem for flex fuel vehicles. The system needs to be diagnosed and reset with a high end scan tool. Get the fuel trims and alcohol content diagnosed before it destroys the engine completely.
@MountainManJoe Thanks for the reply. Yes, I had a mechanic hook it up to his scanner and he noted that the ethanol content was around 92% so we had it reset to factory. Also, I had the infamous sticking lifter and had to tear the top of the motor off to replace the lifters and when I did it I put the head gaskets on backwards and some coolant leak into parts of the engine where it obviously should be. I had to take the heads off again and put new gaskets on correctly. Will a slight bit of coolant in the combustion chamber for a short period of time foul the O2 sensors? I think I am going to replace the cats with the universal ones and replace the O2 sensors as well. This truck has been a real piece.
I wouldn't worry about the O2 sensors unless you keep having problems.
Change the oil + filter to make sure you get all the fuel and coolant out.