Hello all, new member here with an unusual not such a problem anymore situation.
2003 Honda Accord 2.4 5M 257000kms on it. Bought the thing used as a winter beater checked it out drove it around previous owner and I actually drove it around quite a bit, scanned it, ran great outside of an odd vibration between 2000-2500rpm under acceleration (bad axles? Motor mount?) but no codes.
My dad wanted to check out this car that I bought for next to nothing so he took it for a few days and in that time he filled it up with premium fuel (ethanol free) to “clean it out” yes I understand how octane works, but he doesn’t seem to.
When I got it back all was normal, but after a few more days let’s say 1/16th of a tank the check engine light came on p0420 catalytic below efficiency something or other. Cleared the code and it came back after a day or two, then cleared it and it came back within a day and then within a few kms on the third try.
Decided to just ignore it for a while and shop for some lacquer thinner at the same time ;). Commuted with it daily till I was almost out of gas and filled it up regular fuel (10%~ ethanol) after again approximately 1/16th or so of a tank the CEL code cleared itself. It’s been two more days now and it hasn’t come back.
Coincidence? Thoughts? We don’t have emissions testing here anymore so not like it mattered much. And apologies for the novel, figured more details is better than vagueness.
Yeah. The place where he went to get the fuel was probably a co op or something with 75 year old tanks in the ground filled with rust. The catalytic converter only has to read like 10% below optimal efficiency before the oxygen sensor will throw the code.
Ah that wasn’t the case he only goes to chevron or shell, I was thinking it was the ethanol content but don’t enough about how it affects the cats.
Yeah you never know though. It could be as simple as condensation buildup inside your fuel lines and fuel tank that mixes with the gas and makes the car run lean for just a few minutes. The oxygen sensors are very sensitive.