I currently have a 2003 Ford Ranger 4x4 XLT V-6,4.0 liter engine recently my Check Engine Light came on it said Banks No. 1and 2 Too Lean,I have changed my fuel filter (under drivers seat ) spark plugs and wires,oxygen sensors left and right upstream. It still has the problem of stalling,missing,rough idle just running like on its last leg .What do I need to do next??? PLEASE HELP

TxGreaseMonkey

Test/replace the Engine Coolant Temperature (ECT) Sensor, which affects fuel injector pulse width. The ECT Sensor is a temperature dependant resistor (thermistor), whose resistance decreases as the engine coolant temperature increases. It provides a richer mixture when cold, leaner mixture when hot. They become corroded, due to not changing the coolant frequently enough.

$12.99 at AutoZone (SU2301).

Dragonslayer

You most likely have a vacuum leak. One of the more common areas to look for on the 4.0 SOHC would be the intake plenum gaskets. When you have lean codes for both banks like that, its going to be something common to both banks, like un-metered air after the throttle body. Listen for a whistling noise when the engine is running. It could be something as simple as a vacuum hose being disconnected. Try to spray carb cleaner or use propane enrichment to locate where this leak might be.