Resistor based problem

[galanos]

Neel,

On E46 M3, we have experienced the following problem.

Idle engine speed was 1100 rpm. Whenever we tried to lower idle engine speed from 1100 downwards, engine stalled.

Installed brand new idle controller. No good news. Engine speed at idle was 1100 rpm. Does not idle below 1100 rpm. Stalls below 1100 rpm.

Adjusted throttle plates. No good news. Engine does stall if we try to set idle below 1100 rpm.

Checked wiring and sensors and many things.

Found out that the "RESISITOR" was causing the high idle issues.

Removed the 3,2K ohm resistor. And idle is 750 rpm.

So it was the 3,2k ohm resistor causing high idle.

I started putting different resistors and idle is 750 rpm with resistors up to 1,8k OHM.

If I put a resistor bigger than 1,8k OHM, idle goes up to 1000-1100 rpm.

Moreover, if I try to keep the idle at 950-1000 rpm, with resistors bigger than 1,8k OHM, if I blip the throttle up to 3500 rpm and back off the throttle engine dies.

This means resistors bigger than 1,8k OHM cause two problems:
1- high engine speeds @ idle such as 1100 rpm
2- if I try to keep idle at 950-1000 rpm, engine stalls if I rev to 3500 rpm and back off .

Is there a way to cure this issue on caltool? such as inside the crank sensor settings?

[Neel]

What resistor are you talking about?

[galanos]

What resistor are you talking about?

I am talking about the resistor which is installed between the pectel and the engine speed sensors. SQ6 manual instructs to use a 3,2k ohm resistor for the engine speed sensor.

We always installed a 3,2k ohm resistor, for the last 2 years, but we never got aware of the idle issues, cause we have been using high duration cams.

Removed the aftermarket cams, expected idle to be at 700-800 rpm. This is how we found out about the 3,2k ohm resistor bases issues.


Regards,
Galanos

[Neel]

I am talking about the resistor which is installed between the pectel and the engine speed sensors. SQ6 manual instructs to use a 3,2k ohm resistor for the engine speed sensor.

We always installed a 3,2k ohm resistor, for the last 2 years, but we never got aware of the idle issues, cause we have been using high duration cams.

Removed the aftermarket cams, expected idle to be at 700-800 rpm. This is how we found out about the 3,2k ohm resistor bases issues.

This cannot have anything to do with your idle issues. The resistor only effects cranking startup & high RPM signal loss. The only reasonable explanation for your high idle is an air leak or mapping that is wrong so that the engine wants to stall at lower RPMs. The way to check this is simply block off the idle air ocntorl motor. If your idle does not drop, then you have an air leak.

[galanos]

Neel,

there is no air leak. we checked air leaks.

throttle plates are perfect.

Any resistor over 1,8k OHM, idle goes up to 1100 rpm.

Any resistor below 1,8k OHM, idle is perfect at 800 rpm.

Idle rises anytime we use a resistor over 1,8k OHM.

Regards,

Galanos

[Neel]

there is no air leak. we checked air leaks.

throttle plates are perfect.

How? Did you block off the IAC valve like I asked?

[quote][Any resistor below 1,8k OHM, idle is perfect at 800 rpm.

Idle rises anytime we use a resistor over 1,8k OHM./quote]

Interesting. No idea why - all the resistor does is attenuates the crank signal at high RPM so that the voltage doesn't saturate the input. Perhaps someone else can chime in here - I have no idea how altering the voltage output of the crank signal would change idle speed! Are you maintaining perfect 720 sync the whole time?

[galanos]

Yes synch is 720.

[MarcoV6T]

This still doesn't make sense, although I've DBW, the engine idles fine at 750-800 rpm, without any by-pass resistor on the crank sensor.

Maybe it's a hardware problem, do any sensor readings change when changing the resistors?

[galanos]

This still doesn't make sense, although I've DBW, the engine idles fine at 750-800 rpm, without any by-pass resistor on the crank sensor.

Maybe it's a hardware problem, do any sensor readings change when changing the resistors?

Marco, do you have a M3 E46?

[MarcoV6T]

Sorry for the late answer galanos, but no, I've a VW Corrado V(R)6 24V engine.

Did you find any other solution to your problem?

I must say that without the resistor on the crank sensor, I've have now and then a sync error at +5000 rpm, so I'll add a resistor and see what happens(although I just blowup my transmission, it's just too much NM for this standard trans.).

Edit: I just saw your 'lambda' topic, so I guess you find out where the problem lies.

[littleozfella]

HI, Your idle speed problem maybe the fact that is is just your idle motor base position for the rpm, ie at 1100 rpm your bypass valve table is higher than at 750. The engine is probably stalling at 1000rpm with the 3.2k resistor fitted because it maybe over filtering the crank sensor and you could be loosing the signal. Log Engine mode, Crank 1 Voltage Raw (or maybe Crank 1 Inductive voltage, try both) and Cam voltage raw all at about 250hz and see what is happening. Maybe with 3.2k itis loosing the signal, but it is odd that the engine starts OK. Rather than change resistor, check the air gap of the sensor and maybe reduce this gap. 0.5mm to 0.8 I would guess. Also check your Crank exit speed and stop exit speeds to make sure your ecu isnt going into Crank mode when it is idling I usualy use crank exit speed at about 400rpm. Hope i have been of some help..

[Neel]

HI, Your idle speed problem maybe the fact that is is just your idle motor base position for the rpm, ie at 1100 rpm your bypass valve table is higher than at 750. The engine is probably stalling at 1000rpm with the 3.2k resistor fitted because it maybe over filtering the crank sensor and you could be loosing the signal. Log Engine mode, Crank 1 Voltage Raw (or maybe Crank 1 Inductive voltage, try both) and Cam voltage raw all at about 250hz and see what is happening. Maybe with 3.2k itis loosing the signal, but it is odd that the engine starts OK. Rather than change resistor, check the air gap of the sensor and maybe reduce this gap. 0.5mm to 0.8 I would guess. Also check your Crank exit speed and stop exit speeds to make sure your ecu isnt going into Crank mode when it is idling I usualy use crank exit speed at about 400rpm. Hope i have been of some help..

I don't think that the resistor can have anything to do with this for the same reason you said about starting. We've scoped these before and if there's enough voltage to get 720 sync at 300 RPM there's no reason it would lose it at 1000 RPM. I think there's something else going on here; this motor has large injectors and a pretty radical setup - I tuned it and it is not easy to get it to behave at low-loads.

-Neel