Idle control works intermitently....why?

[RazOn]

The idle control doesn't seem to work all the time and I don't know what's causing it.

I'm attaching some screenshots with the settings. You can see the engine is at 1400rpm+ and there is zero correction from both IAC and timing, even though I have them configured for idle control.

For the most part, the engine idles normal, but if I rev it up sometimes the rpm stays high... like in this case. It's like my throttle body sticks (I've tried two throttle bodies with same results). 16% IAC duty cycle normally gives 3-4% throttle body position... In the screen shots it's "stuck" at 9%.

Regardless... why is the ECU not even trying to correct in this case?
Sometimes, when it works properly, I can see the IAC intergral value go down at which point the rpm's drop and the engine stabilizes at the normal idle rpm.

Any thoughts?

[Kamuto]

what car is it? what idle valve? most of them need diode across + and controll signal

[RazOn]

It's '97 VW Golf VR6. The throttle body has a built in idle motor and position feedback. It works by actually opening the throttle... no bypass holes.

My question is more related to software though.
In the 1'st picture below, the "IAC integral" is zero (no correction) even after idling high for a long time.
In the 2'nd picture, the "IAC advance adjust" is also zero indicating again that the ECU is not even trying to correct the idle speed.
So no PID control of throttle and no Spark advance idle control.

Based on the settings I have, the ECU should try and control the idle but something is preventing it from doing so... how do I find out why is not making the corrections?
As I mentioned before.... sometimes it works. Maybe engine speed has to be closer to idle speed before the ECU even attempts to correct?

[Kamuto]

It's '97 VW Golf VR6. The throttle body has a built in idle motor and position feedback. It works by actually opening the throttle... no bypass holes.

My question is more related to software though.
In the 1'st picture below, the "IAC integral" is zero (no correction) even after idling high for a long time.
In the 2'nd picture, the "IAC advance adjust" is also zero indicating again that the ECU is not even trying to correct the idle speed.
So no PID control of throttle and no Spark advance idle control.

Based on the settings I have, the ECU should try and control the idle but something is preventing it from doing so... how do I find out why is not making the corrections?
As I mentioned before.... sometimes it works. Maybe engine speed has to be closer to idle speed before the ECU even attempts to correct?

that idle motor does not works with vems properly.. end of story hook simple 2 wire idle valve and that's all

[Leonhard]

This throttle body integrated idle control works vice versa. Default position of flap is open for max idle and limb home mode.
For idle control, flap has to be moved to close position. Look for the VAG self study guide #173, there's more info about this unit.
Check for proper PWM frequency, flyback diode might stable control behavior too, but first try to get the right (opposite) direction.
Maybe you just have to change the min to max PWM duty allowed values to get it reversed.

[Kamuto]

This throttle body integrated idle control works vice versa. Default position of flap is open for max idle and limb home mode.
For idle control, flap has to be moved to close position. Look for the VAG self study guide #173, there's more info about this unit.
Check for proper PWM frequency, flyback diode might stable control behavior too, but first try to get the right (opposite) direction.
Maybe you just have to change the min to max PWM duty allowed values to get it reversed.

I thought about it yesterday, put it on injector channel and enable dbw, maybe there is possible to control it with it then you will get access to throttle target tables. because in reality that's not solenoid, this is dbw motor, I will play some day with it if I get that throttle on my hands.

[RazOn]

I appreciate you guys's input but I'd like to say this again: this question is not about hardware!

Throttle body control works for me. For example: If I go to "Idle PWM Hardware Settings" and I change the "Min PWM Duty Allowed" from 0 to 10 then 20 then 30% I can watch the throttle body move. It's not linear.... this could be improved, but it works for now.
Most of the times car idles good.


The problem I'm inquiring about is: sometimes the ECU stops controlling the idle, and I don't know why?!
In the screenshots below you can see IAC ON flag is on, but there is no correction made by ecu. Not throttle control and no ignition control.
Engine rpm is steady high at over 1400rpm... I'm expecting to see the IAC Integral at -30 and IAC Advance adjust to -4deg.
Am I wrong about this?

[NOTORIOUS VR]

I appreciate you guys's input but I'd like to say this again: this question is not about hardware!

Throttle body control works for me. For example: If I go to "Idle PWM Hardware Settings" and I change the "Min PWM Duty Allowed" from 0 to 10 then 20 then 30% I can watch the throttle body move. It's not linear.... this could be improved, but it works for now.
Most of the times car idles good.


The problem I'm inquiring about is: sometimes the ECU stops controlling the idle, and I don't know why?!
In the screenshots below you can see IAC ON flag is on, but there is no correction made by ecu. Not throttle control and no ignition control.
Engine rpm is steady high at over 1400rpm... I'm expecting to see the IAC Integral at -30 and IAC Advance adjust to -4deg.
Am I wrong about this?

Because as it's been said, it doesn't work with the OBD2 VW throttle bodies correctly.

The throttle body IAC specific to what you are using is a type of PWM... So while it does "drive" the motor, it cannot control it correctly.  This isn't new.  Your best bet is to forget about it and use a traditional 2 or 3 pin PWM IAC from VW/BMW and plumb that in.  You will have rock solid idle with them (2 wire type will require a diode).

Otherwise you're on your own if you want to deal with the built in TB IAC motor in this application.

[RazOn]

  my question has nothing to do with hardware.

I'll put it a different way. The ecu doesn't know what's connected to it's outputs....right? Even with nothing connected... the software should still work and ECU should send the signals.

When idle speed is outside of dead-band, we should see the IAC duty cycle and timing advance change. I'm monitoring this numbers in VEMSTune and they don't change!

If the numbers don't change, the outputs don't change, and regardless of what's connected to these outputs, no correction will be made.

I'd like somebody to explain why the numbers are not changing (duty cycle and timing)... are there certain conditions that inhibit idle control?
Even if throttle body doesn't work, we should still see timing corrections.


@Kamuto - Idle Control output is mapped to Injector Output 6. What's dbw and how do you enable it?

[Leonhard]

OK, putting aside how you managed to get the hardware working so far.
There's no spark angle on your screen, sometimes idle get stuck caused by highly advanced ignition at this point (ignition map). Try to set "Advance change of max retard" up to 20 (ignore warnings ) and lower "Advance Rate of Change" to 20. This will help lowering rpm and find back to "normal"

[gunni]

RazOn do you have a log of this?
IAC control has been working well since about 2010.

If you want I could teamview into your laptop and have a gander while the engine is running, sometime tomorrow depending on where you are in the world.

[Kamuto]

RazOn do you have a log of this?
IAC control has been working well since about 2010.

If you want I could teamview into your laptop and have a gander while the engine is running, sometime tomorrow depending on where you are in the world.

this throttle
http://c1552172.r72.cf0.rackcdn.com/64071_x600.jpg

it's dbw idle motor
does not works properly with current idle hw logic

[gunni]

http://www.hobbytronics.co.uk/h-bridge-driver-sn754410

shouldn´t be hard to make this work as the controller and control it usign two IAC outputs.

[RazOn]

Thanks for all the input and willing to help guys!
Busy time of the year    but I managed to get in the shop last night and shot some movies to post here. In the process, I figured out the answer to my question!

Under PWM hardware settings there is a "Min PWM Duty Allowed" setting. When the limit is reached (and rpm still too high) the whole idle control algorithm stops, It's not just "clamping" the output.
I was expecting (especially since the IAC On flag was ON) that the algorithm would still work (see the numbers change) just that the output would be clamped between the min and max settings. Anyway... nothing wrong with this. Just different than what I thought.

Now we can talk about throttle body control
The problem for me seems to be that the air intake temperature makes a BIG difference on how much the throttle body needs to be opened and the "Min PWM Duty Allowed" seems to be the MAIN thing that prevents the engine from stalling when the revs are dropping (like revving it in neutral and letting the engine settle).
This setpoint however is not scaled with temperature, so no way to tune it for both cold air and hot air.

This car runs on E85, 1700cc injectors, and liquid (ice) to air intercooler... AND it was like -10deg outside recently. Starting the car, IAC is ~0degC, then once the engine warms up and the underhood temps go up, IAC is ~65deg.
So... let's say I set the min pwm to ~20 which is perfect when running with hot air, and then I open the hood (on turn on the intercooler pump), engine gets cold air rpm's go up and no way to close the throttle body.
If I set the min PWM at 16, good for cold temps, I use the other functions to get good idle and everything works fine until I try to rev the engine and let it settle. When I do that, the PWM drops to the MIn Allowed (16) and the idle control cannot catch the engine, so it just dies.

Now I'll post the videos.

[RazOn]

Here, you can see how idle control normally works for me with fan coming on and off.
The engine has bigger cams (288deg) and I'm trying to idle at 950rpm.
Honestly I'm happy with the way it is in this video... good enough for me
You can see how the idle control algorithm continuously makes corrections.

https://youtu.be/A4MLF9fAZN0