E30 Zone

Could it cause the idle control valve to open fully?

The TPS tells the ICV to "work" when the throttle butterfly is closed, or to "stop working" when the butterfly opens, not sure which way round but that is how it works.

The TPS is three-way: closed, part and full. On closed throttle the ECU will use its idle fuel and ignition mapping along with the ICV to achieve a steady idle.
Part throttle is 'normal' operation, the ICV isn't adjusted, fuel and ignition are mapped according to revs and engine load (from the AFM). If a lambda sensor has been fitted, the ECU will also use the output from this to fine-tune fuel delivery.
On full throttle, the AFM and lambda (if fitted) are ignored and the ECU uses a map that reads only engine speed and is optimised for power.

So it could be possible that if the TPS is 'stuck' on the idle, the ICV could be forced open constantly?

I'm having some terrible trouble with the ICV, and I'm clutching at straws

http://www.e30zone.net/modules.php?name ... c&t=118079

TPS just tells the ECU to go into 'idle mode'; it won't open the ICV by itself. It sounds like your ICV is faulty, to be honest.
Did you lubricate it after cleaning?

I didn't lubricate the ICV, but it seems to turn very freely in both ways, and when 12v is applied it will snap open and closed easily.

The ICV seems to work perfect on the bench, but when re-connected to the car it fully opnes as soon as ignition is on. Is there a check I cn do with a multi meter to confirm that the ICV is getting the correct opening and closing signals. I am aware that these are pulsed signals so cannot really be checked?

I've also just this moment checked the tps switch for continuity when closed / open. The TPS is ok.

You haven't told us what age and model of car yet!

It's an '89 320i, but from zoner help so-far, I am thinking it is just a borken ICV...

http://www.e30zone.net/modules.php?name ... c&t=118079

On my 88 320i the ICV shuts on ignition (you can hear it buzz) and opens when cranking. It is a modulating spring return valve I believe, thus the ECU can (I think) adjust it for a smooth idle / tickover. That said the tickover on mine is awful, barely 600rpm when hot and just 800rpm when cold. On LPG it actually stalls on tickover most times...
A common area of problem I think...

I tested my ICV with a multimeter and found that the continuity could be lost when 'jiggling' the valve. The overall resitance was as I read it should be (40ohm between outer pins, 20ohm between inner and either outer).

I've just had it apart - it's essentially just a 2-way motor that can turn 90 degrees, no springs.

I cleaned the contacts and bent them slightly to ensure a better contact, but still get the loss of continuity.

I am assuming that the closed and open voltages are constantly 'fighting' each other to get the desired opening - I think my closed coil / contact is slightly broken, meaning that the closed voltage doesn't stand a chance against the force opening the valve. I'm also pretty certain the position of this valve is NOT fed back to the ECU, so it cannot compensate.

Please correct me if I'm talking balls.

jslot wrote:Please correct me if I'm talking balls.

Pretty much all correct!

interestingly the ICV in the motronic spec says "fail safe". how they can say that when it is not spring return is beyond me, but yeah, it is definantly as you described : basic and open loop.

Maybe the fail-safe claim is with respect to a failed sensor that might have an effect on the ICV.

In this case the ecu would know that a sensor had failed, and would 'electronically' fail-close the ICV.

I agree, with no feed back, for the ICV itself to be described as fail-safe, it would have to be sprung.

Also,

Where did you find your info on the Motronic specs?

http://www.opel-scanner.com/files/DME_1.1_1.3. pdf

found as citing 10 on here:

http://en.wikipedia.org/wiki/Motronic

very good read...

For the purposes of those searching historic posts to try and solve similar probs:

It was the ECU at fault, replaced and fixed

http://www.e30zone.net/modules.php?name ... c&t=118719