Idling fuel consumption, Polo 86c AAV

Hi there.
I'm afraid my question might not be entirely appropriate for this forum, but before I go to a dedicated 'Motortalk' section...

Question:
Is it possible to determine, using VCDS, how many liters of fuel per hour are consumed by the above-mentioned vehicles when idling?
Or otherwise, with minimal technical effort?

Modern engines consume approximately 1 liter of fuel per hour when idling, and I suspect that my Polo consumes 'significantly' more.

Can this be done with VCDS, or at least roughly estimated somehow?

Best regards, Frank.

Part number for the engine control unit (ECU)?

Best regards, Rainer.

Considering the engine size, I would estimate a consumption of between 0.6 and 0.8 liters per hour, depending on the engine load.

AAV (air volume control valve) -> 1.3L, 40kW, Bosch MonoJet system (approximately models from 1987-1994) -> Only fault codes are available, so no reading with VCDS or similar tools.

Hi!

Well, those blink codes are a good starting point.
You can also measure the lambda sensor voltage.
Or check the car's exhaust emissions with a measuring device.

The way we used to do things 20 years ago.

It might be helpful to write a little more about the problem. In my experience, I've never had anyone complain about excessively high fuel consumption when idling.
It usually went something like this: "The car uses way too much fuel, it's smoking, and leaking from the exhaust."
These were often simple electrical faults in the engine control unit (e.g., a tangled mess of wires at the temperature sensor).

Where can I find the engine control unit (ECU) number?
Stickers or over VCDs?

The car consumes 5.8 liters per 100 kilometers when driving at 120 km/h on the highway.
In the city during summer (short distances), fuel consumption is between 7.5 and 8 liters per 100 kilometers.
In the winter, I often get 9 liters per 100 kilometers, especially with very short trips and unfavorable traffic lights.
Since I fixed the lambda sensor heating system, it's been a little less.
My girlfriend delivers newspapers, and I've gone with her a few times to help transport the papers.
Since it was cold, I kept the engine running.
You can almost watch the fuel gauge drop as you drive.
I need to refuel again to get accurate readings.
Based on my feeling, it's consuming significantly more than 1 liter per hour when idling...
Therefore, my question is whether this effect can be roughly and inexpensively determined quickly.
'Filling the tank completely, letting it run for a few hours, and then filling it up again would be the most accurate method, but I don't really want to do that...'
Best regards, Frank.

Hi!
Gasoline engines are generally less suitable for short trips or newspaper delivery routes because they tend to pump an excessive amount of fuel into the engine if it doesn't reach its operating temperature of approximately 86°C. This is programmed into the engine control unit.
A diesel engine would be better in that case.

Alternative approach:

For example, if the thermostat isn't working correctly and the engine is therefore constantly too cold (which happens quite often), this problem will be exacerbated.
You should check if the coolant temperature is normally hot, and that the heating system is working properly. If you suspect a problem, measure the temperature at the water flange using a pyrometer.

Here's how I would start if I had to deal with this problem.

F B wrote:

Where can I find the number of the engine control unit? Stickers or over VCDs?

Liest du eigentlich auch mal die Antworten die man dir schreibt?

Bertil wrote:

... nur Blinkcodes, also kein auslesen mit VCDS oder ähnlichen Tools.

Quote:

The car consumes 5.8 liters per 100 kilometers when driving at 120 km/h on the highway. In the city during summer (short distances), fuel consumption is between 7.5 and 8 liters per 100 kilometers. In the winter, I often get 9 liters per 100 kilometers, especially with very short trips and unfavorable traffic lights.

Everything sounds largely normal for an EA801 CARBURETOR ENGINE!

This engine is essentially a carburetor engine that has been converted to an electronic fuel injection system using the Bosch Monojetronic. This was a cost-effective solution at the time to implement a catalytic converter with controlled emissions.
These engines were running extremely rich and completely over-oiled. Unfortunately, nothing on these engines is adjustable.
The engine control is a simple alpha-n regulation with lambda feedback. It doesn't use a mass airflow sensor or anything similar.
It is largely an analogous arrangement.

Quote:

Based on my feeling, it's consuming significantly more than 1 liter per hour when idling...

That's also perfectly normal. For the engine, I would estimate a value of roughly 1.2 to 1.5 as being within the normal range, just like with the carburetor predecessors.

If you're looking for a defect in this fuel injection system, you're in for a challenge. The throttle body is the central component and, essentially, everything that can break down. These parts were very prone to failure, often breaking and being extremely expensive to replace.

Many mistakes were made:
DK unit defective/oiled, connectors oiled, temperature sensor (for the air in the DK section) oiled.
Unfortunately, the vacuum line for the K-series engine ended directly above the throttle body and was also located right next to the connector for the electronics.

Where can I find the number of the engine control unit?
Aufkleber oder über Vcds?

Do you actually ever read the answers that people write to you?

... nur Blinkcodes, also kein auslesen mit VCDS oder ähnlichen Tools.

Yes, but apparently it works after all.
While it doesn't allow for a complete data read-out, it does enable the retrieval of individual values and the clearing of error codes.
Best regards, Frank.

I just filled up the tank and did some calculations.
Given the relatively low mileage and the 5 to 6 hours of idling time, the fuel consumption becomes less significant.
If I factor out the fuel consumption at idle, then the overall consumption is acceptable.
Best regards, Frank.

What are the values?

F B wrote:

Yes, but apparently it works after all.

Something doesn't quite add up there.

The AAV is a monojetronic engine. The TCU (030906026..) that you are showing here, however, is a monomotronic unit. It can be read out (with very limited functionality).

Hmm, who knows who might have 'McGyvered' something at some point?

Current consumption values from memory:
Approximately 420 kilometers driven with nearly 43 liters of fuel consumed, minus 6 hours of idling time.
Something around 8.8 liters per hundred kilometers, which is normal for typical short trips and stop-and-go traffic.
Best regards, Frank.