Idling Speed Control: 130 HP PD Yesterday

Yesterday, I had the pleasure of reading out a 130 HP PD engine. Everything seemed fine so far, but one thing seemed a bit suspicious: In the idle speed control, there was a deviation of 2 mg/stroke between cylinder 1 (-1 mg/stroke) and cylinder 4 ( mg/stroke). Cylinders 2 and 3 were normal (around 0 mg/stroke). However, the car didn't jerk, and it drove normally. Why is this? Normally, something like this should cause jerking, right?

Best regards, WarLord.

WarLord wrote:

Usually, something like that should make itself known by jerking or shaking, right?

I think the stuttering only occurs when the system is ramping up.
That can happen, but it doesn't have to.

Hm, okay. Wasn't there also something about having to replace the PD elements if they deviate too much? Or was that only the case if there's a jerky movement?

Best regards, WarLord.

Hello WarLord!

The values only indicate that there are differences between the individual cylinders. However, the active control compensates for these differences, so that (ideally) no more vibrations occur.
If all cylinders were supplied with the same amount of fuel injection, then an uneven torque output would result.

Regards,
Alex.

Jupp is correct, donalexo!

A deviation of up to 3mg per cylinder is permitted!

Okay, then I probably had incorrect information.

I'm glad that everything seems to be fine with me, as our PD (presumably referring to a medical test or measurement) shows very little difference between the cylinders.

Best regards, WarLord.

Mine also only shows very minimal values around 0, evenly across all 4 cylinders. Strangely, even during the minimal warm-up roughness...