Quick TPS question

[Rhyse30]

e30 M20B25 engine. (swapped into a 320i)

I was testing my TPS last night. I have continuity between pins 1 and 2 (or 2 and 18 according to other instructions I've read...), the left and middle pin when looking at the TPS. Once I slightly open the throttle it clicks and I don't have continuity anymore. This is fine isn't it? But when I tested pins 1 and 3 (left and right pins) nothing happens at around 2/3 open, I don't get any resistance reading.

Am I meant to see some kind of change at 2/3 open?

My car is having some starting problems so that's why I took off the throttle body to see if that carbon canister plug in the throttle body has failed and creating an air leak (still not sure where this plug actually is as I couldn't find it).

I found that, after the last time I took off the TPS, I screwed it back on, just after the 'click' for closed throttle body, so the ECU would be getting a reading that the TPS was slightly open. Would this cause my engine start oddly?

I hope this makes sense and any ideas welcome.

[Brianmoooore]

At low to mid throttle, there should be no continuity between any of the TPS pins, and there should never be continuity between 1 and 3 at any throttle position.
At wide open throttle there should be continuity between pins 2 and 3. This is by a simple leaf and cam switch, so won't be in such as precise a position as when the idle microswitch switches.

[Rhyse30]

Thanks for the reply Brian.

I had another look last night and it turns out the last time I took off the TPS to clean it, I attached the TPS to the throttle body but I didn't rotate it enough for it to read closed circuit at closed trottle. So the TPS was sending a signal to the ECU telling it the throttle was part open when it was in fact fully closed, meaning no signal was being sent to turn on the the ICV when at idle.

Car seems to start fine when cold and warm now.

My only concern is, if the ICV wasn't engaging when I started the car causing the car to stall or have very rough revs when I pressed the accelerator pedal, after around 20-30 seconds, the car ran pretty good, even when idling at junctions and so on. Does this mean I have an air leak somewhere that caused the engine to keep running, even though the throttle was completely closed and the ICV was not engaged?

Again, hope this makes some kind of sense.

Thanks!

[Brianmoooore]

It's important that the TPS operates as soon as the throttle leaves its stop, consistent with reliably switching back again when the throttle is closed. If the throttle opens too far before switching, you will get a flat spot when accelerating from closed throttle.
Any sign of the throttle stop having been moved from its factory setting?
What do you mean by "ICV was not engaged"? The M20 ICV is different from most, in that it is powered open and powered shut, by what is effectively two opposing electric motors.
An engine that "sorts itself out after 20-30 seconds" would lead me to consider a leaking injector or two, leaving the inlet plenum full of petrol vapour that has to be burnt off, or an out of spec. 'blue' temp. sensor.

[Rhyse30]

Right ok. Thanks Brian.

By ICV not engaged, I mean it was shut. I take it when the throttle is completely closed (continuity between pin 1 and 2 on the TPS) the ECU opens the ICV?

When I cleaned the TPS last time, I adjusted it on the throttle body incorrectly so when the throttle body was completely closed, the TPS was not showing continuity. Would this mean the ECU thought the throttle was part open, delivering more fuel, but in actual fact the throttle was actually closed meaning there was more fuel but no air flow as the throttle was shut and the ICV was closed?

I do have some suspicion the throttle stop has been moved. The head of the screw has sheared off leaving just the thread. So someones has had a go at it.

I've tested the blue temp sensor with a cold and hot engine. The reading are consistent with the figures on the wiki.

Not had my injectors cleaned yet, that's next on the list.

Since setting the TPS correctly so when the throttle has just opened there's no continuity, the car has started fine. But even with the engine cold it idles at about 700-800 rpm. Shouldn't it be around 1100 when cold then 700-800 when warm?

Also, when I was fault searching I took a look at the plugs to see what condition they were in. The plug in cylinder no.2 had a very small gap. I didn't have my feeler gauges handy but it was significantly smaller than the rest. The plugs are around 4-5 month old and were all gaped correctly when I put them in. What would cause this?

Thanks again!

Rhys