My 91 F150 has been surging when idling. I checked the codes and got an 11 on the continuous codes and 53, 63, 34, 81. I decided to look at 53 and 63 first since they had to do with the throttle position sensor. I checked the voltage at the connector before it reaches the TPS. My book said that it should have around 5.0 volts with the KOEO, it read 0.0 volts. I wanted to check the other end of the supply voltage but so have been unable to find a schmatic showing the path of the wiring.

Does anyone have any suggestions for a schmatic or happen to know where the other end of the supply voltage orginates.

 

The TPS is supplied with the VREF (~5.00 VDC) signal from the computer (PCM).

Use this for reference: Fuel Injection Technical Library » Throttle Position Sensor (TPS)

A schematic:

courtesy of oldfuelinjection.com


Some handy info from Seattle FSB on another forum:

1988-1991 TPS Wire Colors
VREF - Orange/White
SIG RTN - Black/White (My 1990 is actually Red/Gray)
TP SIG - Dark Green/Light Green


1992-1996 TPS Wire Colors
VREF - Brown/White
SIG RTN -Gray/Red
TP SIG - Gray/White


Motorcraft TPS Wire Colors
VREF - Orange
SIG RTN - Black
TP SIG - Green

 

Thanks, do I need to take the TPS off of the throttle body to check resistance and voltage or can all of that be done from the wiring harness. I thinking that I may have checked the voltage in the wrong location.

 

You leave the TPS connected to check for voltage. Use some pins to pierce the wires. For resistance check it will have to be disconnected. Personally I rely more on the voltage test than resistance check.

 

Checked the TPS, it was out of range. Replaced it idling much better now. The only code other than 11with the KOEO test that I'm getting now is 33 which is the EGR. Checked it out its getting 5 volts and seems to be acting correctly when checking resistence. 3.5 k ohms without vaccum and .8k ohms with 10" of vaccum applied. Any ideas on the code since the EGR checks out.

 

I prefer voltage checks, but at least you know the EVP sensor is changing value. Now you need to see if the vacuum line running from the intake manifold is hooked up. Then verify it is hooked up to the EGR Valve Regulator (EVR) then onto the EGR valve itself.

The EVR is modulated on/off by the PCM. Check the electrical connections.

For reference: Fuel Injection Technical Library » EGR Vacuum Regulator (EVR)