Predictably runs good for 20 miles, then acts like it's not getting enough fuel?
I'd be looking at the fuel tank vent.
Easy test--loosen the gas cap, drive it more than 20 miles. If it runs good...you're likely pulling a vacuum in the tank as you drive, because the vent is somehow plugged. Loosening the cap provides a different way to vent the tank.
I'd be looking at the fuel tank vent.
Easy test--loosen the gas cap, drive it more than 20 miles. If it runs good...you're likely pulling a vacuum in the tank as you drive, because the vent is somehow plugged. Loosening the cap provides a different way to vent the tank.