The person I got it from said he accidentally put oil treatment in fuel tank. Rough idle.
My car has 170000 miles.
My car has an automatic transmission.
Hi there, thanks for writing in. I suggest you have the fuel pump checked for loss of pressure. The additive the previous owner added in may have damaged the pump and or the filter. If you first remove the fuel filter, check it and if there’s anything wrong, you should replace it. You may have to have fuel added to the fuel tank if there was less than a quarter tank of fuel when additive was added. This will dilute the additive. If the pressure is still below specifications, then I recommend replacing the fuel filter and pump.
If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make any repairs as needed.