[Trevor]

Set your meter to a resistance in ohms scale covering up to 5,000 ohms.


ADJUSTING AND CLEANING THE THROTTLE POSITION SENSOR.

In order to adjust the TPS the manual says to measure voltage at the TPS by inserting meter probes into the plug at the ECU plug connection. In order to accomplish the feat at the TPS itself, therefore without tying yourself in a knot under the dash, you will require, best of all one of those dress making pins with a nice thin shank and a knob on the end, or a thin needle. Also a meter to measure 0.5 volts d.c..

The TPS comprises a potentiometer, incorporating a conductive plastic element, presumably used in a voltage divider configuration, as three wires come from it. There is a plug and socket close to the unit so that it can be easily removed for servicing. At this plug the wires are --- black ground and one end of the resistance element, red the other end and white the wiping contact.

Holding it with pliers, stick your pin/needle right through the white insulated wire, so that you can clip your meter lead onto it to make measurements. A fine pin will not damage the conductors as they will spread and there will be no significant damage to the insulation. Measure between the wiper, i.e. white wire and ground by connecting to the engine, or battery negative.

If you remove the unit, stick the pin in before replacing it, as it is much easier to do on the bench. Don't forget to pull it out when you have done the deed.

Now from the book :-- 1. Connect all connectors. 2. loosen TPS fixing screws. 3. Turn ignition on. 4. Adjust TPS position, (i.e. rotate the complete assembly), while throttle valve is confirmed FULLY closed, to specified voltage, using a volt meter. 5. tighten fixing screws.

The voltage is specified as within a tolerance of from 0.45 to 0.55 volts. You should have no trouble in setting things at exactly half a volt.

Before removing the TPS or altering the original setting it is a good idea to mark the mating castings with a scratch so that one can check on the adjustment, before and after, as a matter of interest. It is always nice to know if the effort expended has in fact improved things.

CLEANING AND CHECKING.

If the unit is removed, it is easily checked with an ohm meter for smooth operation or otherwise. Evan without dismantling the unit a spray with CRC or similar cleaner and a work out will do wonders. The resistance end to end ( black to red ) should measure very close to 5000 ohms. Measuring between white and red or black should show a smooooooth change in resistance when moving the control shaft over full distance. Blips will indicate trouble.

With the unit in place, a voltage check on the output as the mechanism it is operated while connected and energised, will also give an indication of possible intermittent contact. Again using a needle or pin to make a connection can be helpful. A smooth change in voltage should be recorded.
A meter with a bar graph will show up short duration faults much better than a normal instrument, digital or analogue, as both have an inherent time delay before indication is registered. This factor should be taken into account but should not deter those without sophisticated gear.