I've got a '94 del Sol with a B18C1 with an OBD1 P72 ecu.

When I first got the car (and before I knew it needed premium gas) I filled up on regular for one tank and got a code 43 (fuel supply problem). I then realized it had to have premium and filled up on that ever since. That was about 2 years ago.

Since then I've filled up at pretty much the same Shell gas station and used premium gas every time. However, I just recently moved to a small town out in the country. They have a Shell so I decided to make that my usual fill up spot. However, firs tank of gas I throw a code 43 after about 30 minutes of highway driving. It's happened twice now in three trips. I also noticed pinging (detonation). I'm starting to wonder if this small town gas station is not being careful (or out-right scamming) about mixing regular in the premium tanks. But, before I go telling them they're gas sucks (and see if they have a reasonable explaination for this), is there anything else that could possibly cause a code 43? I would doubt it would be anything else, like fuel pump going out. It started happening pretty soon after using this new station.

Thanks for any help.

 

it was my fuel filter when i got that CEL

 

Code 43 can also be the primary O2 sensor, not just fuel supply system.