I've had this code forever on a test pipe and I have emissions due this month. I changed my OEM cat back in and it threw the code, the cat hasn't been on in a year or two so I'll reset the code tomorrow and see if it'll simply go away on its own since the cat just got back into business. But to the real question, has anyone ever had a P0420 and run E85 to have the code go away (after a reset)? There's an E85 station half a mile from my work and that would be a sure shot to get emissions done with if possible lol...

 

DO NOT RUN E85 IN YOUR CAR! The fuel system and components will not tolerate it, and the fuel pump will not send enough pressure for the engine to run properly. You will have more serious issues than a bad cat.

 

Indymac is correct. Don't ever run E85 in that car.

The fuel system will not be able to deliver enough fuel, the car will run lean and destroy itself. E85 needs considerably more fuel flow through the injectors to get the mixture correct for proper operation. You could be lucky that the car may not start at all if you filled it with that ethanol crap.

I have seen several Ford chassis motorhomes with V10s lose ALL compression from the severe detonation from the lean condition when customers misfuel w/ E85. Al the intake valves "tulip" and the pistons end up with holes in them. I've also seen two Dodge 5.7 engines chuck rods through the block after the pistons disintegrated from all the detonation. These vehicles were operating under heavy load and climbing steep grades when they let go.

 

Didn't think about volume, guess i'll run E(85/3) whatever that is for emissions. Thanks for the warnings