95 3.8L NO START (lean?) FIXED!

[plutonius]

Do you have a Windstar 3.8L that is running lean or will not start at all? Perhaps it is lean because of a fault in a sensor circuit. I had a friend's 95 Windstar that would not even start. The fan came on low-speed whenever the key was turned on. 3 shops worked on it with no results except towing bills. Problem was the "differential EGR pressure sensor" which is on top of the engine on the driver's side. Original units made of cast metal and the exhaust system generates water as a by-product, which caused corrosion in the sensor. The sensor shorted out, and this made the reference voltage for all the sensors wanky. Specifically, it made the temp sensor read hot by dragging down the sensor reference voltage which is a low current feed from the ECU to several sensors. The voltage to the ECT sensor was about 2 volts with the sensor disconnected, the ECU sees this as a very hot engine, resulting in a very lean conditon. NO CODES, NO CHECK ENGINE LIGHT, no troubleshooting chart showed this as a possibility. Try metering the voltage across the 2 pins of the ECT connector with the sensor disconnected and key in the run position (not running) should be 5 volts. If not, start disconnecting sensors until it gets back to 5 volts (and I would start with the DP sensor......). Local Ford dealer said "It shouldn't cause that", so I took the thing apart and verified it was shorted to ground internally. New sensors have a plastic case so they can't short out this way. Hope this helps someone!