Idling Fuel Consumption: Cold vs. Warm (MFA)

Hello!

My 96kW TDI (ASZ/ERF) shows a current fuel consumption of 0.6 (sometimes 0.5 l/h) on the MFA display during cold starts, and 0.8 l/h when it's warm . I'm not entirely sure if it was like this before, but I recently had a new engine installed due to idle vibrations.

According to my technical understanding, the opposite should be true (higher fuel consumption with a cold engine than with a warm one), so I'm surprised every day and wonder if VW also installed a new control unit. Is there actually a way to determine whether the control unit has been replaced? Are there any numbers or something similar that are linked to the engine numbers?
Originally, the vehicle was manufactured in February 2003, but the engine, transmission, and clutch were installed in March 2003.
My suspicion is that perhaps something has been changed on the engine control unit side, such as fuel injection quantities or timing parameters, to eliminate the vibrations during the warm-up phase (which are now GONE).

How does it work with the power consumption display during the initial heating phase for you?

Regards,
Thomas.

Thomas TDI130 wrote:

My 96kW TDI (ASZ/ERF) shows a fuel consumption of 0.6 (sometimes 0.5) liters per hour on the instantaneous display of the MFA during cold start , and 0.8 l/h when it is warm

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My AXR shows a flow rate of 1-1.2 liters per hour when warm, and 1.5-1.8 liters per hour when cold.

I'm not entirely sure if it was like that before, but I recently had a new engine installed because of the idling vibrations.

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Wow, it seems like Volkswagen really went overboard with that fix, or maybe the situation was so dire that an engine replacement was necessary.

According to my technical understanding, the opposite should be true (higher fuel consumption with a cold engine than with a warm one). Therefore, I'm surprised every day and wonder if VW also installed a new control unit.

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It should consume less energy when it's cold.

...
My suspicion is that perhaps something has been changed on the engine control unit side, such as fuel injection quantities or timing parameters, to eliminate the vibrations during the warm-up phase (which are now GONE).
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If the engine control unit (ECU) has been modified (as in my case), then replacing the engine is highly questionable, or you might have made a complete overhaul to avoid further problems. In that case, it would be advisable to get a new ECU.

At least your problem has been resolved, which is certainly a good thing.

Hello Bertil,

'I'm actually quite surprised that there's such a significant difference in performance between the TDI engines with power outputs ranging from 100 to 130 horsepower. Do you have an explanation for this?'

At least your logic is correct (colder than warmer), because something might not be right with my ad , OR NOT?

Zum Motortausch: Es ist ja ein leidiges Thema, aber ich glaube Du hattest ja damals vor Monaten meine Postings verfolgt, weißt also dass bei meinem alten Motor alles mögliche unternommen wurde bis hin zum Nockenwellentausch der nix brachte. VW HAT ein Leerlaufvibrationsproblem bei den PDs. Nur so ist der Motortausch zu erklären, sie wussten einfach nicht weiter. Das zeigen ja auch die Berichte vieler anderer PD-Fahrer, zB nicht nur VWs sondern auch Seats. Es gibt nur keine Lösung des Problems und man muss schon sehr nerven und drohen, bis das Problem eben behoben wird (momentan nur durch Motorentausch möglich). Wenn man sich nicht beklagt, wie das bei vielen der Fall ist aus welchen Gründen auch immer(stört nicht oder wegen Automatik oder...) passiert selbstverständlich auch nix. Das führt bei VW natürlich dazu, dass Sie dieses Problem von der Prioritätenliste nach unten verschieben. Allerdings häufen sich jetzt schon Rückmeldungen, in denen Leute sagen, dass es sie erst nicht störte, inzwischen aber schon, evtl auch wegen Intensitätssteigerung. Wer sagt übrigens, dass die Ursache (die nicht bekann ist) ein 'Spatz' ist ?. Vielleicht wundern sich alle vibrierer eines Tages, dass Ihnen der Motor um die Ohren fliegt (ich habe die Rattermarken an meiner Nockenwelle gesehen)... But of course, everyone has to decide for themselves whether they want to 'vibrate' or not; you're right about that.

Do you know if it's possible to determine whether the engine control unit (ECU) has been replaced, and if so, how? Also, can you infer the production date and location based on the engine number?
I would like to know if it was replaced, but the dealer didn't know, because the car was in WOB (presumably a specific location or department), and they are very secretive about that.

Regards,
Thomas.

Thomas TDI130 wrote:

Hello Bertil, "I'm actually quite surprised that there's such a significant difference in performance between the TDI engines with power outputs ranging from 100 to 130 horsepower. Do you have an explanation for this?"

The 130 model might be more tightly tuned near the tolerance limit, which leaves less room for software adjustments. The 100 model, on the other hand, offers more flexibility in terms of software tweaking.

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At least your logic is correct (colder than warmer), because something might not be right with my ad , OR NOT?

Yes, I agree.

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... Do you know if it's possible to determine whether the engine control unit (ECU) has been replaced, and if so, how? Also, can you infer the production date and location based on the engine number? I would like to know if it was replaced, but the dealer didn't know because the car was at the inspection station (WOB), and they are very secretive about that information.

"Each STG (steering gear) has a production date printed on it. If it's the original STG, it should be up to 6 months older than your car; if it's newer, it will have been replaced."

Hi,

My ASZ (presumably a document or record) from July 2002 shows the same behavior.
The cold water flow rate is displayed as 0.6 L/h, while the hot water flow rate is shown as 0.7-0.8 L/h.