3.2 Surging Idle

[sidebp]

Originally Posted by proporsche

besides all the control checkings ..can you see if you still have this plug in your AFM?It goes on from the bottom of the AFM .If it is still there the fuel mix was not adjusted for a long time if ever..

It's not there - thanks.

[sidebp]

Originally Posted by ischmitz

Is there a chance that someone messed with the throttle stop position and/or idle switch position? The mechanical stop defines where the throttle valve rests when the accelerator isn’t pressed. In a normal setup the throttle return spring pulls the valve against this mechanic stop and then shortly thereafter the mechanism actuates the idle micro switch.

If someone changed the micro switch position to where it holds the throttle valve open too much this could cause your issue where there is simply too much air coming through the throttle body.

Check the following: With the engine off gently start applying throttle by pushing the throttle lever where the cable connects to the throttle body. You should first hear the micro switch disengaging and very shortly thereafter the throttle valve starts opening. When releasing you should feel the throttle valve settling against the mechanical stop and then very shortly thereafter the micro switch gets actuated.

The micro-switch activates after about 1mm movement, the revs then rise. When releasing the throttle slowly it hits the stop and then the micro-switch clicks.

[mysocal911]

Originally Posted by sidebp

I wound the screw right in and the idle dropped from around 1,200rpm to 950rpm - it was stable for about 5mins and then minor surging started (not as severe).

So surging only occurs when the ICV is connected now, right? Can you now achieve a steady 800 RPM idle by adjusting the ICV without the connector?
If so, it's time to have the DME ECU tested!

[sidebp]

Originally Posted by mysocal911

So surging only occurs when the ICV is connected now, right? Can you now achieve a steady 800 RPM idle by adjusting the ICV without the connector?
If so, it's time to have the DME ECU tested!

Connected it also holds a steady low idle with screw fully wound in, after about 5mins it starts to fluctuate but less aggressively. I'm assuming the delay is temperature related.

[mysocal911]

Originally Posted by sidebp

Connected it also holds a steady low idle with screw fully wound in, after about 5mins it starts to fluctuate but less aggressively. I'm assuming the delay is temperature related.

So at last your problem is fixed, i.e. all parts normally connected, right? Glad you fixed it!

[sidebp]

Originally Posted by mysocal911

So at last your problem is fixed, i.e. all parts normally connected, right? Glad you fixed it!

Definetely better but feels like a workaround - presuming screw shouldn't be wound in all the way and idle still surges as it warms.

Still going to see about getting co2 checked.

Thanks for all the inputs, I've learned a ton.

[sidebp]

Hi,

Happy New Year.

Bit of a thread resurrection but I have a quick question as finally the week has come where I can take my car to a local specialist.

Is it safe to drive the car with the ICV disconnected when I take it to the garage? Reason for asking is that I have unplugged the valve, manually set the vane position to part closed and I can get a buttery smooth idle with no pulling - this feels a lot safer than having to ride the brakes and deal with the on/off jolting I experience when the valve is plugged in.

I plan to leave early morning to avoid traffic but being a touch paranoid I don't want to do any other engine damage from running it too rich/lean or risk it cutting out mid drive (I've deliberately set the idle slightly faster at around 1k RPM).

[sidebp]

I got the car to the garage with no issues.

Unfortunately, the garage (Impact Bumper specialist) believe the ECU is faulty. Big bills pending

[ischmitz]

Where are you located, U.K? Here in the U.S. it'd be pretty straight forward to get the ECU tested and if required repaired.

[sidebp]

Hi,

Yes in the UK - seem to be a few repair shops but not sure on who is reputable.

I've been doing some research about alternatives to the Motronic system as there are few available, it appears CANEMS have discontinued their direct replacement. Are there any other alternative ECU should I not be able to get it repaired?

[ischmitz]

sibebp,

Any Motronic box can be repaired. I've had boxes on the bench that were submerged in water for extended periods of time or had internal "fires" and even these were brought back to life. In terms of economics I don't see any alternative that would come even close to getting the DME repaired. Even a homebuilt Megasquirt would set you back more than buying a good used DME outright. And that is before labor...

[sidebp]

That's positive - I wasn't sure if Motronic repair was a dying art. Will do some research on some of the UK forums.

[wazzz]

Pretty sure you'll find a good pro in UK. Otherwise, we have decent people here in France too, but you'd have to ship your box across the Channel and with Brexit and all, that has become less than easy.