Technical Stalling when using windows

[koalar]

I don't have a idle controlled car to test

I found

This on the forum

One car was running fine

I have no idea what this means though

@Mike1alike also gets similar results and is still active on the forum

Although a Punto it would ateast give use an understanding of the numbers

 

[jasimog]

SOLVED

The solution was to use carb cleaner in the throttle body. I believe the stepping motor / idle control intake was dirty and so the TB could not react fast enough to changes in electrical load, causing the car to stall.

It now works as expected. Idle control is steady, even under high electrical loads such as holding both electric windows against the stops at the same time, even with headlights and rear window demister on. I can see that the stepping motor demand signal in MES is really reduced, so the mechanism is not working too hard to maintain idle speed, when previously it was off the scale.

I'll gather more data over the next few days and then write a more comprehensive post with the symptoms and solution.

Thank you for everyone's helpful replies, especially @koalar.

 

[jasimog]

Summary

I promised more detail on this fault. As a reminder, the car is a Fiat Panda 2006 1.2 Dynamic with cable throttle.

This is the throttle body (TB) assembly:

There are three connections to the TB:

• the throttle cable, which has a spring in the mechanism to close the throttle/return to idle when the accelerator is released
• the throttle potentiometer, which provides a reading of the throttle position to the ECU
• the idle stepping motor, which controls idle speed as dictated by the ECU

At idle the throttle cable spring pressure keeps the main throttle air intake closed, and fine idle control is maintained via the idle intake and the stepping motor, which adjusts the idle speed in line with the control signals passed by the ECU. This is variable with factors such as aircon on/off and electrical load taken into account. Baseline idle speed is usually 750 rpm.

Symptoms

The fault was that the car often stalled at idle, especially when under electrical load (e.g. switching on rear window demister, opening front windows). This only happened when the engine was fully warmed up (when cold the ECU raises idle speed which masked the symptoms). I checked the basics, like alternator voltage and this was fine (14.1V). I had recently fitted a new battery, and the spark plugs / ignition cables were new.

I tested the idle control with MES (which I have since registered, but these tests can be done with the free version). This is done on the Actuators tab:

This test raises idle speed twice (to close to 2000 rpm), and was successful. This showed that the stepping motor could work correctly when instructed by the ECU (i.e. the TB itself was probably OK). But the fault was still present.

I next monitored the stepping motor at idle on the Parameters tab:

The 'Idle actuator (Step motor)' line tells you how hard the ECU is 'driving' the stepping motor. I now know that 83 in this example is far too high.

The solution was to clean the TB with carb cleaner (see previous post). I focused on the idle intake which leads to the step motor mechanism. Almost immediately this worked, and after a 10 mile test drive I checked the car again:

The idle actuator setting is now 51, and even under electrical load such as raising/lowering both front windows to the stops I couldn't stall the engine and the actuator reading never went above 60.

In summary, my diagnosis was that the idle control / stepping motor mechanism was dirty or gummed up which meant that it couldn't react in time to the ECU's demands, causing the car to stall. It's been fine for a week now, so fingers crossed this is a permanent fix, and I will add cleaning the TB to my maintenance routine

I hope this helps someone else. Apologies if exact terminology isn't correct.

 

[koalar]

Well done in updating the thread

No doubt it will not be long before this data will help someone else, these cars are now just getting to that age, where wear and dirt are causing problems