Service light on no power engine hesitates when

I have a 1997 Expedition and I replaced every sensor and went through all of this. I even changed out the O2 Sensors. The parts guy said I had 3. The problem is that I trusted that person and realize I had 4. I had this hesitation problem and almost stalling out and had 2 codes for Bank 1, Passenger side is Bank 1. There is an Upstream O2 Sensor there that cannot be seen unless you remove the wheel and pull back the plastic fender well. There is a Ford Technical Service Bulletin saying that the A/C drain run directly onto this O2 Sensor and the sensor fails. The way to fix it is to buy a GM PVC tube and modify it to reroute the drain to the 7 o'clock position and replace the O2 Sensor. www.rockauto.com has the O2 Sensors for $20.69 and the PVC Tube is $8.99 at Autozone. I did this and after 3 years of going freaking nuts it is running like a rand new truck, no hesitation, no almost stalling out, acceleration is back and reliable and towing the RV is a pleasure now. I hope all of this helps and I hope that others in my position happen upon this post so that they do not lose as much hair and I and do not waste as much money replacing parts that are not bad in the first place.
This TSB article is being republished in its entirety to update the Service Procedure.

ISSUE:
The Malfunction Indicator Lamp (MIL) may illuminate and Diagnostic Trouble Codes (DTCs) P0133, P0171 and/or P1131 may be stored in memory. Additionally, there may be one or more of the following driveability symptoms:

Hesitation
Stumble
Surge
Miss
Rough idle
Near stall or stall at idle
Detonation on acceleration
This may be caused by cold condensate from the A/C system dripping onto the Heated Exhaust Gas Oxygen (HEGO) sensor causing thermocycling of the HEGO sensor .

ACTION:
Divert water from dripping onto the sensor by installing a fabricated drain tube to the end of the A/C drain. This should reroute the water and reduce the possibility of the above conditions occurring. Refer to the following Service Procedure for details.

SERVICE PROCEDURE
Fabricate a drain tube from PCV Vent Tube (F85Z-6758-BA). To create the drain tube extension, remove the rubber cylinder from the plastic tube and discard. Cut the plastic tube (Figure 1).

Remove the transmission fluid level indicator.
Remove the right front wheel.
Remove the right front fender well splash guard.
Clean the area around the transmission filler tube and then remove the tube. Be sure to cover the hole using tape (or equivalent) to prevent contaminants from entering the transmission.
Replace the right front HEGO Sensor (F88Z-9F472-AB) and leave the connector disconnected.
Modify the PCV vent tube (Figure 1) to make a drain for the A/C condensate drain.
Using needle service light on no power engine hesitates when - icon1.pngref="http://www.fordf150.net/forums/#">pliers or equivalent, stretch the drain tube elbow fitting for ease of installation.
Refer to Figure 1 and fabricate a tool using a 61x2.5 cm (24x1") I.D. pipe as shown.
Lubricate the elbow with water.
NOTE: DO NOT USE SILICONE TO LUBRICATE THE ELBOW AS IT WILL FALL OFF.



Using the tool, install the modified drain tube at the 7:00 position toward the frame (Figure 2).
Clean the transmission filler tube.
NOTE: BE CAREFUL NOT TO DAMAGE THE O-RING AS THIS COULD CREATE LEAKS OR ALLOW CONTAMINATION INTO THE TRANSMISSION.



Lightlservice light on no power engine hesitates when - icon1.pngte the transmission filler tube O-ring with petroleum jelly and reinstall the tube into the transmission.
Torque the bolt to 11-14 N-m (8-10 lb-ft).
NOTE: MAKE SURE THE BODY SIDE HEGO WIRING CONNECTOR IS IN THE LOCATOR HOLE IN THE BACK OF THE HEAD.



Connect the right front HEGO sensor connector.
Start the vehicle and verify water flow direction. Make sure no condensation drips onto the exhaust manifold bolt.
Reinstall the right front splash guard.
Rservice light on no power engine hesitates when - icon1.pngthe right front wheel.
Clean and reinstall the transmission fluid level indicator.
NOTE: DEALERS MUST ALSO PERFORM TSB 97-26-19 TO REPROGRAM THE POWERTRAIN CONTROL MODULE (PCM).




PART NUMBER PART NAME
F85Z-6758-BA PCV Vent Tube
F88Z-9F472-AB Heated Exhaust Gas Oxygen (HEGO) Sensor

Read the code. Hesitation problem is usually caused by a bad TPS, or any sensor connected along with it.