Re: 2001 Ford Ranger misses and poor fuel mileage
P0135 and P0141 are O2 sensor heater circuits. P0301 Is Cyl. #1 misfire, P0403 is secondary air injection malfunction, P1432 canister purge solenoid, P1537 is IMRC stuck open. Some of these are caused by others. Clear the codes and the run the truck and retest to see what may be the main problems. The O2 sensors and some of the others could be caused by a poor ground. Check all the grounds on the engine to make sure they're all connected and clean.