Cold start problem: Incorrect injection timing?

Hi,

ich habe ja seit September einen Audi 100 mit AAT-Motor im 'Fuhrpark' (s. Signature).
Since then, I've also been experiencing the following cold start problem (which I mentioned earlier).
At temperatures between approximately 5 and 10 degrees Celsius (41 and 50 degrees Fahrenheit), the engine starts without any issues (in under 2-3 seconds), but then shakes for a few seconds before abruptly settling into a smooth idle.

Today I had the diagnostic trouble codes read at a VW dealership: nothing found!
BUT I think there might be a problem with the start of injection - here are the measured values:

Ad group 0.
(Engine idling, coolant temperature not below 80 degrees Celsius)

Field 1: Motor speed - Setpoint: 43...36 - Actual: 36
Field 2: Injection start - Target: 45...60 - Actual: 39 !!!
Field 3: Accelerator pedal position - Target: 0 - Actual: 0.
Field 4: Injection amount - Target: 5...25 - Actual: 8
Please provide the text you would like me to translate from German to English.
Please provide the text you would like me to translate from German to English.
Field 7: Coolant Temperature - Setpoint: 80...36 - Actual: 68
Please provide the text you would like me to translate from German to English.
Please provide the text you would like me to translate from German to English.
Field 10: Air Mass Intake - Target: 41...75 - Actual: 41

Question: So, the injection start timing is incorrect, right?
Is this therefore also the cause of the cold start problem?

Sure, here's the translation:

'Here are a few more guidelines:'
- No loss of performance.
- excellent cold start performance.
- Excellent cold starting performance even in sub-zero temperatures (with preheating).
- The timing belt was replaced during the purchase (reason?).
- hardly any soot (the 5-cylinder engines already produced a bit more soot anyway).

Thank you for your help!

P.S.:
Thanks again to MichaelII, who recently added the measurement data for the Methusalix AAT engine to the error database!

Hi,
My AFN showed exactly the same behavior before I adjusted the injection start. Take the 1.5 hours and set it up properly. You'll probably be just as excited about the starting behavior of your engine as I am right now .

Hi,
I agree with Andy, but I also have AAT.

Hi,

Well, that's quite amusing!

Because the timing belt was replaced by the authorized dealer at the time of purchase.
Das sollten die doch eigentlich hinbekommen, ohne nochmal nachjustieren zu müssen...
Probably, a 1993 5-cylinder TDI is already considered a classic car for which no one is trained anymore.
Nevertheless, I'll let the team know about it again - it should actually be changed for free.

Hi,

Problem gelöst! Thank you!

Since the start of the injection process, it starts up perfectly and *runs smoothly, like a cat purring* .

Sure, this isn't exactly a groundbreaking discovery – a faulty fuel pump is bound to cause starting problems.
BUT it's perhaps interesting that it only started poorly at certain temperatures.
Normally, it would run very cleanly with good performance and be quite quiet (but now it responds to the throttle more directly).
Therefore, in such cases, don't just look for defective temperature sensors or glow plugs, but also test the fuel injection timing.

Hi,

Problem gelöst! Thank you!

Since the start of the injection process, it starts up perfectly and *runs smoothly, like a cat purring* .

Sure, this isn't exactly a groundbreaking discovery – a faulty fuel pump is bound to cause starting problems.
BUT it's perhaps interesting that it only started poorly at certain temperatures.
Normally, it would run very cleanly with good performance and be quite quiet (but now it responds to the throttle more directly).
Daher: In solchen Fällen nicht nur nach defekten Temperaturfühlern oder Glühkerzen suchen, sondern Spritzbeginn testen.

Hey,
That could be the solution to my problem. The starting behavior hasn't improved much with the new glow plugs, but it seems to prefer the stutter-free start-up (AEL) at these temperatures. According to Bosch ESi, the ESP is likely faulty or not properly configured.

Best regards from Bielefeld.

Peter.

Markus H. wrote:

Problem gelöst! Thank you! Since the start-up sequence is initiated, it starts up beautifully and *runs smoothly, like a cat purring*

.

Hi Markus,

I'm now starting to pay close attention . Three forum members have kindly sent me a private message, urging me to move the start date forward. Perhaps it really is the solution to my cold start problem

Wie wurde Deine Pumpe eingestellt?? Too early?

I will, however, proceed systematically: temperature sensor, flow control valve, and then the pump. I am someone who needs to understand everything . This can have its advantages and disadvantages. At the very least, I don't want to mask other causes with a premature start of the pumping process!!

Best regards, Christian.