steam in the exhaust

[bronconcious]

Thread update:

Finally broke down and had it towed to a mechanic as now the power went completely dead when the ignition switch was turned to START, I just don't have the time to put into it before the snow hits. Read the codes with a Snap-On code reader and it specifically told him the O2 sensor is showing as defective (lean); hence the dumping of fuel when the truck warms up and goes into closed-loop.

I always suspected the O2 sensor as one of the problems as it is one of the few sensors which is active only when the vehicle gets warm. I just didn't want to believe it because it was replaced last year and the Ford OEM one was working for 20 years.

The difference is I replaced it with an ebaY Borg-Warner sensor, this one specifically:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=350217373145&ssPageName=STRK:MEWAX:IT

Yes it is cheap, but I expected it to last more than a year! This time I went with a high quality, direct fit, Bosch O2 sensor. So far the truck is running great, I'll let you know if anything changes. Thanks for all the help.

Well the problem came back after a few minutes of driving so I guess the O2 sensor itself wasn't the cause as expected. I'm beginning to think that it is a wiring problem, possibly with the O2 circuit. Can anyone explain the route of wires from the O2 sensor to the ECU? Unfortunately the Haynes isn't very specific.......

 

[IMenriched]

found in the Tech Library...hope it is what your looking for
http://www.therangerstation.com/tec...es/Diagrams_ElectronciEngControls2_9_1of3.JPG
http://www.therangerstation.com/tec...es/Diagrams_ElectronciEngControls2_9_2of3.JPG
http://www.therangerstation.com/tec...es/Diagrams_ElectronciEngControls2_9_3of3.JPG

 

[bronconcious]

found in the Tech Library...hope it is what your looking for
http://www.therangerstation.com/tec...es/Diagrams_ElectronciEngControls2_9_1of3.JPG
http://www.therangerstation.com/tec...es/Diagrams_ElectronciEngControls2_9_2of3.JPG
http://www.therangerstation.com/tec...es/Diagrams_ElectronciEngControls2_9_3of3.JPG

Thank you for the links, would you happen to know the route of these wires in the engine bay ie. along the intake manifold, down the cowl, etc...? I would like to trace the wires from the o2 sensor to see if there are any breaks or shorts.

 

[bronconcious]

Update

So I checked for continuity in the wiring from the (02, coolant temp, air intake temp) sensors --> ECU pins and all check out good with low resistance ~.1ohm.

1) The 02 & coolant temp sensor have been replaced, but the air intake temp is old. Checked the resistance on it and it was open (OL) and covered in carbon. Cleaned the carbon off and it showed resistance in spec. Would this cause my stumbling/running rich in closed loop?

2) I am guessing that the ECU reads the air intake temp sensor only in closed loop, can someone confirm this?

3) Also, the coil in the ECU relay (pins 1&2) reads OL when the ignition is off and closed when the ignition is on, is this normal as well?

4) What other sensors that have control of the fuel mixture in closed loop should I be looking at?