>The bypass valve has an "open gap" on the bench or when not energized. Once on car and running, it is wide open.

Sounds OK, except it shouldn't stay wide open when the car is warm. Something is telling the ECU to raise the idle, when it doesn't really need to.

> Haynes says that 'counter clockwise' is toward the connector. I assumed they meant with the TB in my hand looking at the TPS. On my car, that would be rotation toward the driver's side.

I would make the same assumption. Bentley says to turn it counter-clockwise until it stops, but not so far that the throttle starts to open, then lock it down. Then, listen for the "click" just as the throttle begins to open. If it doesn't click, the TPS is bad.

>My TPS has three pins, #2, #3 and #18.

Bentley does not identify pin 18. I'm looking at both my Bentley and Haynes manuals, and I'm a bit confused here. Bentley doesn't lable the pins, and the Haynes schematic was drawn in such a way as to make the draftsman's job easier (avoiding crossed wires as much as possible).

Wait a minute while I run down to the garage and see how this thing REALLY works...OK, I'm back.

Let's try this. The TB is in your hand, and you're looking at the TPS, connector pointing down. Let's relabel the pins. Note: if the TB is in the car, you can peel back the rubber shroud on the connector and probe the contacts through the back of the connector (ignition OFF).

Pin G - ground, the center pin, black wire, connected to system ground.

Pin I - indicates throttle closed at idle, yellow/white wire connected to Pin 2 on the ECU, it's on your right (down/toward engine if the TB is in the car)

Pin W - indicates wide open throttle, blue/white wire connected to Pin 3 of the ECU, it's on your left (up/toward fender if the TB is in the car)

You should see continuity between I and G with the throttle closed, and open all other times. This matches what you are calling Pins 3 and 18.

You should see continuity between W and G at WOT, and open all other times. This matches what you are calling pins 2 and 18.

It sounds like your TPS is working and adjusted correctly.

>Do you know if there is a rheostat in my TPS that should be sending a VARYING signal to the ECU? If the TPS is simply a switch, how does the ECU receive the position of the throttle to regulate and match the fuel flow thru the injectors?

In LH2.4, the TPS is just a switch. In LH 3.1, it is a rheostat. The main input for the ECU is the AMM. Most of fuel flow regulation is based on the amount of air entering the engine. The air/fuel mixture is fine tuned based on engine temperature, engine load, engine speed, and exhaust gas content, and possible other things. The goal is optimum efficiency under all conditions.

In LH2.4, the TPS tells the ECU when the engine is at idle, so that the ECU takes over engine speed regulation. When the TPS indicates WOT, the mixture is enriched for better acceleration.

In LH3.1, the variable resistance gives provides the ECU a more accurate indication of what the driver wants the engine to do , based on throttle position. It knows where idle and WOT are, and can use the throttle position to make adjustments at cruise.

For high idle with a warm engine, I would check the engine temperature sensor, the O2 sensor, cold start injector (could be leaking when it should be closed), the A/C input signals (ECU raises idle if A/C is on), RPM/crank position sensor (unlikely), fuel pressure regulator (unlikely), and AMM (unlikely). Faulty connectors/wiring for those components is also likely.

If you want to fix this yourself, you REALLY need the Bentley manual. It has complete diagnostic instructions. It also documents additional ECU diagnostic modes that are not in Haynes. You obviously have mechanical aptitude and know how to use a Volt/Ohm meter - that's all you need. Testing the fuel pressure regulator requires a pressure gauge, but a new FPR is cheaper and easier.

Hope this is helpful!

-Ron