Please Help with a hard problem
08-26-2012, 08:54 PM
#1
Please Help with a hard problem
Can anybody come up with anything that would make the computer keep turning the fuel pump on and off over and over with the key just tuned on once with the engine not running?
It is like you keep turning the key on and off over and over but you are not.
Or it is like the computer is running the power up self test over and over.
It is a 1995 F150 5.0L 4R70W.
Tried three different computers so it is not the computer.
Changed the PIP sensor in the distributor three times.
Replace the MASS sensor.
KOEO self-test comes back with a 111.
CM comes back with a 111.
KOER reports Knock sensor not detected.
Check the voltage from the TPS as the throttle was slowly opened, .8VDC CT and 4.5V WOT.
Ref voltage 5.0V
When you start the engine it will start normal and if you let it idle the CEL will flash three times and the engine will rev from 750 RPM to 1500 RPM with the IAC going going from 38% to 58%. The high rpm will continue until you put it in gear then the truck goes back to idle.
Truck will lose power with the CEL/MIL light on when leaving stop sign and you have to floor the throttle to get power and turn off the CEL/MIL.
But this does not seem to set a code.
I though I had a good handle on these trucks but this one has me scratching my head.
Any help would be appreciated.
It is like you keep turning the key on and off over and over but you are not.
Or it is like the computer is running the power up self test over and over.
It is a 1995 F150 5.0L 4R70W.
Tried three different computers so it is not the computer.
Changed the PIP sensor in the distributor three times.
Replace the MASS sensor.
KOEO self-test comes back with a 111.
CM comes back with a 111.
KOER reports Knock sensor not detected.
Check the voltage from the TPS as the throttle was slowly opened, .8VDC CT and 4.5V WOT.
Ref voltage 5.0V
When you start the engine it will start normal and if you let it idle the CEL will flash three times and the engine will rev from 750 RPM to 1500 RPM with the IAC going going from 38% to 58%. The high rpm will continue until you put it in gear then the truck goes back to idle.
Truck will lose power with the CEL/MIL light on when leaving stop sign and you have to floor the throttle to get power and turn off the CEL/MIL.
But this does not seem to set a code.
I though I had a good handle on these trucks but this one has me scratching my head.
Any help would be appreciated.
08-31-2012, 01:52 AM
#2
Senior Member
My suggestion would be to find all the harness grounds - remove the bolts - clean body / frame and terminal & hardware with wire brush and reinstall. I would then look at the harness connectors for the Alternator, and for the ignition module make sure everything is clean and making good contact. Verify, Full voltage available. If nothing is found then I would drop the column and look at the ignition switch - not the key - the electrical switch . Then I would look at the neutral safety / selector switch on the trans (If automatic). Shot in the dark but Last resort I would replace ignition module and plug wires...... Possible EMI issue???
Best of luck;
ToddsSS, Benton, AR
Best of luck;
ToddsSS, Benton, AR
08-31-2012, 07:10 AM
#3
Thanks for the reply but I have the problem fixed as of yesterday.
I think this can only happen to 1992-1995 5.0L engines as they are wired different than any of the other Ford engines.
The 5.0L uses the SIG RET wiring and the other engine use a different ground for the O2 sensor.
What the problem was that the heat from the exhaust manifold cooked the wires for the O2 sensor right near the starters wires brake out wires on the harness. I by passed the entire starter harness to solve the problem. I ran the bypass wiring from the plug at the battery all the way to the O2 sensor. My bypass wiring was from another 1995 5.0L truck that I had parted out. So it was just plug and play and a few wire ties. I do not know what wires in the starter harness was shorting to cause all of this as I am not going to undo that starter wiring harness and dig into it.
I think this can only happen to 1992-1995 5.0L engines as they are wired different than any of the other Ford engines.
The 5.0L uses the SIG RET wiring and the other engine use a different ground for the O2 sensor.
What the problem was that the heat from the exhaust manifold cooked the wires for the O2 sensor right near the starters wires brake out wires on the harness. I by passed the entire starter harness to solve the problem. I ran the bypass wiring from the plug at the battery all the way to the O2 sensor. My bypass wiring was from another 1995 5.0L truck that I had parted out. So it was just plug and play and a few wire ties. I do not know what wires in the starter harness was shorting to cause all of this as I am not going to undo that starter wiring harness and dig into it.