Low RPM & Oil Pressure: Troubleshooting Guide

Hello,

According to Julian's reports, I also temporarily adjusted my LL (low load) RPM to approximately 830. The ASZ engine sounds more relaxed at idle, and you can still start the car without giving it any gas as usual, and let it roll in each gear.
After the initial adjustment period, I'd like to keep it set up this way for now, provided that the on-board electrical system doesn't shut down in winter due to insufficient alternator output (there's a voltmeter on board).

What's concerning me (again) is the even lower oil pressure. In my Golf with the AFN engine, I was sometimes only getting 1 bar of oil pressure at 903 rpm when the engine was warm. The Polo doesn't have an oil pressure gauge.

I've now seen in a label file for the ASZ that the automatic transmission cars should have a lower idle speed (790 - 870 rpm) than the manual transmission versions, which have an idle speed of 860 to 940 rpm.
According to this, the engine should be able to handle it, provided that the automatic versions are not built differently in detail (regarding components like oil pump, etc.), and also that they are suitable for long-life oil (i.e., 0W-30).

Can anyone confirm this?

I've installed additional instruments.

The oil pressure is at...
5W-40 full synthetic oil at an oil temperature of approximately 95 degrees Celsius, and a water temperature of 90 degrees Celsius at idle speed of 900 RPM, resulting in only 1.0 bar.

I have no idea how that is harmful, but it's exactly like that.

Since the oil pressure switch activates at engine speeds below 2000 RPM only at significantly lower pressures (less than 0.3 bar), and that's how the manufacturer installed it, there shouldn't be any problems.
The oil pressure warning sensors (I have two of them) are also specified by the manufacturer.

Hello Ulf,

That's a great and, above all, useful thought you've had. Healthy oil pressure is essential, not just in TDI engines. That's why I'll be installing an oil pressure gauge soon.
I can only comment on the minimum idle speed (LLDZ) of my AHU automatic transmission. Normally, it runs at 861 RPM as a minimum value. Through adaptation, I was able to reduce the LLDZ to 819 RPM, but no lower. This value of 819 is only achieved when stationary in D gear; in neutral, it runs at 840 RPM. The reason for the adaptation was potential fuel savings. Since I mostly drive in city traffic daily, constantly maintaining the low idle speed under load (e.g., in D gear in front of a traffic light) consumes a lot of fuel. The engine has to constantly fight against the automatic transmission, because I don't shift into neutral at every traffic light. This 'fighting' is compensated for by increased fuel injection, which also increases consumption.
When I reduced the LLDZ (low-speed driving mode) to only 840 RPM, the 'fuel consumption' as measured by group 15 (liters per hour) almost halved. The engine also rocks much less, which is very pleasant.
Everything is good and fine, but my main concern is the oil pressure, which has likely decreased. Since I don't have an oil pressure gauge yet, it's difficult for me to estimate the actual value.
I highly doubt that the automatic and manual transmission motors differ in their construction, but they likely do in their control units. Therefore, I would like to know how far the low load driving zone (LLDZ) can be reduced in a manual transmission AHU engine.

Perhaps someone among you who has an oil pressure gauge installed could, for testing purposes only, bring the LLDZ (Low Load Drive Zone) to 800 RPM (this doesn't necessarily require channel adaptation, but rather a slipping clutch) and read the oil pressure. Ideally, this should be done at various oil temperatures.

Thank you in advance.

Best regards, Georg.


P.S.: @Ulf, I remember you posted somewhere how to calculate fuel consumption in liters per 100 km using VAG-COM, but I can't find it anymore. I don't have a Multifunction Display (MFA). I would appreciate it if you could send me a private message about it.

Georg-TDI wrote:

@Ulf, I remember you posted somewhere how to calculate fuel consumption in liters per 100 km using VAG-COM, but I can't find it anymore. I don't have an MFA (Multifunction Display). I would appreciate a private message from you about this.

Hmm, I suppose you remember the reversed calculation direction: "MFA display -> injection quantity".
Okay, I'm ready. Please provide the German text you want me to translate into English.

Haha, you're worrying too much. If your oil level is at the maximum mark, then the oil pressure will be sufficient under all operating conditions of the engine.

The oil pressure sensor in my AWX only recognizes values above or below 2 bar, and the pressure rises very quickly when starting the engine. Once the engine has started, the oil pressure exceeds 2 bar at that moment.

2 bar?!

I doubt that's true.

What's your problem? When it's cold, the oil pressure can quickly reach 7 bar, and 2 bar is perfectly fine.

If you don't believe it --> SSP

Julian wrote:

The oil pressure sensor in my AWX only recognizes values greater or less than 2 bar, and these values are reached very quickly when starting the engine. Once the engine has started, the oil pressure is above 2 bar at that moment.

Hmm, do you have a direct indicator for the switch?

My AI only triggers an alarm if the 1.5 bar (approximately) pressure switch is not closed at 1500 rpm, which essentially acts as a pressure-per-revolution warning.

Below 1500 rpm, the engine control unit (ECU) doesn't care about the oil pressure – I could drive with zero oil pressure (like if the oil pump was broken) without any warning until the engine seizes, as long as I don't exceed 1500 rpm.

I'll probably install a temporary additional oil pressure LED that is directly connected to the switch...


Which SSP are you actually referring to?

@Julian
I highly doubt that as well!

'2 bar pressure at 900 RPM with standard xW 40 oil at operating temperature? No, I don't believe it!'
Normally (and only with a lot of luck), you won't reach these 2 bar until around 1300-1500 RPM when using hot oil.

When it's cold, the high oil pressure is maintained at a maximum of approximately 4.8 bar (experts may correct me) by a 'pressure relief valve'. Therefore, your 7 bar should never be reached.

Either you've modified your oil pump, are using a high-performance oil (like xW 60), and your pressure relief valve is faulty, or your oil pressure gauge is malfunctioning.

Perhaps Bertil is the right person to consult here, as he is still an active motorsports enthusiast and needs to be familiar with oil pressure limits.

Best regards, Georg.

In the Audi 80 B4, there were always two oil pressure switches installed:

One switch reacts at 0.3 bar, and the second switch reacts at 0.7 bar.

The oil pressure warning light illuminates when the oil pressure drops below 0.3 bar, or when the engine speed exceeds 2100 RPM and the oil pressure falls below 0.7 bar.

Depending on the specific model and equipment (additional instruments), the gear shift points may vary slightly. Also, the oil pressure warning contacts have a tolerance of +/- 0.1 bar (according to the marking on the switch).


And I think that even the newer models don't have completely different minimum oil pressures; for example, 2.0 bar (possible from 2000 RPM, but not at idle).

Belief and knowledge are two fundamentally different areas. I know that the tire pressure for my car is 2 bar. It may be different for other cars, and I don't deny that at all.
But I think it's quite a stretch to compare a long-distance runner like the B4 with my relatively new car.

Even the Mercedes R107 had a nice pressure gauge in the speedometer. Even at idle when warm, it would read over 2.0 bar. Just tapping the accelerator and it quickly went above 3 bar. And that was from the year 1978...
The behavior was the same with the '91 Golf2 GTs. *If we're already rearranging antiques here.*

My ALH engine also had a two-stage oil pressure switch (1.5 bar and something else, if I remember correctly), while the AWX has a one-stage switch.

I don't know what VW was manufacturing at Ulf's 9N facility; other manufacturers have different concepts. We already knew this from the intercooler.

@Georg: I hope that as a Diplom-Ingenieur (Which field of study?), you have more to offer than just fortune-telling.

Okay, I took a closer look at my oil pressure switch.

Its casing is brown, and I believe the pressure setting should be between 0.5 and 0.8 bar (I couldn't read it without turning it around – is the pressure indicated on the casing?).

In any case, the engine will not start with 0W30 oil when the temperature is warm, as it fails to engage after approximately 5 seconds at starter motor speed (starter motor directly powered from the battery positive terminal, ignition off).

Unfortunately, without knowing the specific engine and conditions, it's impossible to say exactly what the pressure should be at 840 RPM idle according to VAGCOM.

@Julian
I think I missed something about "antiques"...
I've now taken a closer look at your "brand new" AWX. For example, I installed it in a 2002 Passat.
Oil pressure switch 038 919 081 C.
0.55 - 0.85 bar, housing color brown.
It's screwed into the oil filter housing.

@ulf
is engraved on the bottom of the hexagon. You have to rotate it to be able to read it.

I dug out an old oil pressure switch.

Here is the number 028 919 081.
0.15 - 0.35 bar, housing color: blue.


The data can be found below.

faz wrote:

I dug out an old oil pressure switch: Here is the number 028 919 081. 0.15 - 0.35 bar, housing color: blue. Below, you can read the data

.
Okay, I'll check mine out too and see what's going on.

ulf wrote:

faz wrote: I dug out an old oil pressure switch: Here is the number 028 919 081. 0.15 - 0.35 bar, housing color: blue. Below, you can read the data . Thank you, I will also take mine out and have a look.

Could it also be that?

Quote:

Oil pressure switch 038 919 081 C. 0.55 - 0.85 bar, housing color brown