1995 F-350 7.3 POWERSTROKE Looses Power - Ford Truck Enthusiasts Forums

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1995 F-350 7.3 POWERSTROKE Looses Power

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Old 03-01-2012, 10:05 PM
Mike's Big Ford Mike's Big Ford is offline
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1995 F-350 7.3 POWERSTROKE Looses Power

The 7.3 looses power and then may regain minutes later or not at all. Check engine light comes on when power is lost, and goes off when power is back. Have checked and changed fuel filter in bowl, drained water. Was told it was a faulty TPS, changed the pot switch. This seemed to help for a short time. Had the codes read while it was running decent, PO236, PO122, PO123, PO603, and PO221 were shown. Was told the accelerator assembly needed changed because the one switch was not working. This was when it was running good. I have found that when the pedal is pushed down the actuator on the on/off switch had not been made buy the arm on the assembly. I put a shim in between the switch and the arm and restarted it and it ran great. I thought I found the problem and this woul be a simple fix. I tried to start it the next day with the shim in place and I got the same old problem of which seems like half the power. I try to rev it up but can only get about 2000 on the tach when it does this. While I was thinking and searching for something else to check it ran ruff and then great 4 times in about a half an hour. Where can I get a code reader since I don't want to chance taking it on the road until I find the problem. Any help would be greatly appreciated. Thank you!
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Old 03-01-2012, 10:20 PM
glovemeister glovemeister is offline
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A P0122 code means that the the car's computer has detected that the TPS (throttle position sensor) is reporting too low a voltage. On some vehicles that lower limit is 0.17 - 0.20 volts (V).
A code P0122 may mean that one or more of the following has happened:

TPS not mounted securely
TPS circuit short to ground or another wire
Faulty TPS
Damaged computer (PCM)

code PO236 which is turbo boost sensor A circuit perf
Look at the Map Sensor, and the hose leading to it for damage/leaks, and also the orange 'cross over hoses' on the intake.. Could be a bad sensor/hose, intake/boost leaks, circuit/pin issues, 'possibly' the turbo.. Take a look into the turbo 'inlet' at the compressor blades as well for damage.. If you have a gauge, check the boost pressure for a 'minimum' of 12PSI at the MAP connection on a road test/WOT.
Diagnostic Trouble Code (DTC) P0123
Throttle Position Sensor High Voltage

Knowing the Circuit:

Controlling the idle speed taking the throttle body itself is what the purpose of the MTIA (Main Throttle Idle Actuator) is.
The throttle is particularly devised for low opening angle (05, 195).
The features of the airflow differ for low and high opening angles.
This circuit has a gradient of the mass air flow function of TPS which is lower for small angles that allow it to be more accurate while handling the idle speed control.
A classical Bowden cable actuates mechanically the idle speed throttle.
A voltage signal that changes in proportion to the throttle plate angle is catered by the throttle position sensor (TPS).
It will be seen that the signal voltage will change from about nearly 5.0 V at idles to about 0.2V to 0.4 V at wide-open throttle.
The TPS is one of the most indispensable inputs needed by the ECM for fuel control and other functions such as idle, wide open throttle, deceleration enleanment, and acceleration enrichment.
p0603 is a keep alive memory reset code that usually appears when a chip is changed or removed , doesnt mean pcm is bad(but it could).
P0221 says "Throttle/Pedal Position Switch B Circuit Range/Performance"

If you have a tuner many of this issues can be caused by something like that. I'd pull your tuner and see if they go away.
Second, I would open up your steering column as a wire on the overdrive on/off button on the end of the shift lever could be rubbed and or shorting out.

For a reader I would suggest you purchase this: Riffraff Diesel: AutoEnginuity Total Ford Enhanced Bundle

You will need a laptop to load the program on and use the scanner, but it reads everything the sensors do. You need the total ford enhanced bundle as our trucks are technically not OBD2 compliant, they use I believe a CAN System. Same idea, it just requires a specialized scanner to pull the codes. Buy once and cry once I love my scanner and would gladly pay the $350 for it again.
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