Hey Scotty! I have an 90' Ford and am getting a KOER 41 for HEGO (HO2S) sensor voltage low / system lean. I have triple checked for vacuum leaks, I've checked for misfire via pull plug wires, I've clean MAF and Air filter, but I can't seem to figure this "lean" issue out. Please help! Thank You for everything
Well have the vehicle smoke leaked checked first lean is off in a vacuum leak like an intake manifold or something. If not that even a clogged fuel filter or a weak fuel pump can cause lean too. Check those next