Audi 1Z Power Loss: Troubleshooting & Solutions

Hello,

bin neu hier und lese das Forum auch schon seit geraumer Zeit. Habe mir vor ca. 4 Wochen einen Audi 80 B4 Bj. 94 mit 1Z Motor gekauft, der keine richtige Leistung hat. Da ich das gleiche Modell mit einer LL von 270tkm bereits besitze war ich der Meinung den Fehler leicht zu finden. Trugschluß, hier meine bisherigen Aktivitäten: Tausch des LMM, NHG, STG, KAT inkl. Hosenrohr, ESD, Dieselfilter, Steuerventile für AGR und Turbo, AGR; Überprüfung und Reinigung des Ansaugtrakts, LLK inkl. Schläuche; mehrmalige Überprüfung der STZ. Alles owithout success.
Even after purchasing a diagnostic interface with VAG-Com (shareware) and following the systematic troubleshooting steps described in the forum, everything appears to be fine. However, the correction value for the 3rd cylinder is +3.7. A friend suggested that this could indicate a lack of compression. The lack of power is mainly noticeable at low engine speeds. It sounds somewhat as if not all cylinders are firing, like in a gasoline engine. During driving, the vehicle slightly jerks when accelerating. From a subjective feeling, it seems to improve at higher engine speeds, but the car doesn't exceed 150 km/h.
Does anyone have any other ideas about this?

Hi tdi-fan,

How is the KW screw doing?

Let's measure the compression then.

And I hope that wild swapping frenzy wasn't a complete waste of time.

m;

Hello,

Thank you for the quick reply(ies) first.

Okay, a compression test is already scheduled for this week. If that's the issue, it would be quite unfortunate (the car has a full service history and 155,000 km on the odometer).

I had ruled out the KW screw because I repeatedly checked the speed limiter (STZ) and took test drives in between, and the speed limiter always worked correctly. Or have I misunderstood something?

Could it possibly be the pump?

Best regards, V.

What's the mileage on your new car?

Hello,

As mentioned in the previous response: 155,000 km mileage and well-maintained service history. I was just able to test the compression:

15.5
2. 15.9
3. 15.2
4. 14.6

According to my colleague from VAG, everything is within the acceptable limits.

Best regards, V.

Evening.
das was du da postest ist das Verdichtungsverhältnis??? Das sollte aber bei 19,5:1 liegen. Wichtiger ist der Verdichtungsdruck in den Zylindern und da sollte der 1Z 25 bis 31 bar haben. Die Verschleissgrenze liegt bei 19 bar, max. Difference: 5 bar!

Best regards, Robert.

tdi-fan wrote:

I was just able to test the compression: 15.5 2. 15.9 3. 15.2 4. 14.6 According to my colleague from VAG, everything is within the acceptable limits.

Perhaps for a gasoline engine, but a diesel engine would likely have difficulty starting with this (see also the response from LZ).

-> Measurement error / incorrect scale inserted?

@ LZ

How does one measure the compression ratio "from the outside"?

The only thing that can be measured is the pressure, and that pressure is higher than the compression ratio due to the temperature increase during compression.

The compression can only be measured either through geometric measurements or through volumetric measurements using incompressible media (e.g., water). However, firstly, no one will actually do that, and secondly, it's not something anyone is interested in.

I think:
Either the car is junk because the readings are genuinely inaccurate, or there's a systematic error, like a "faulty scale."

m;

PS: Compression pressure also has a unit of measurement - or does 15.2 cows per square meter (SCNR) count as one?

Do 15.2 (something) perhaps correspond to non-SI units used with a TDI engine, because it was an American-made compression gauge?

Given the relatively similar values of the cylinders, I would initially assume that there was a measurement error and that the compression is likely fine.

Hello,

I had also wondered about those values myself (I only know them from the older 1.6 D engines; but that was quite a while ago...).
War aber ein Kompressionstester von VAG. Wird sich morgen klären, dann hakt der Kollege nochmal nach (bzgl. Scale).

In my opinion, such a loose engine shouldn't be difficult to start and shouldn't produce excessive smoke – but that's not the case; it starts immediately (at the current temperatures). I'll comment again once I have more information.

Assuming that the compression is okay, could the problem possibly be the ESP? If so, I would then replace it on Saturday.

Best regards,

V.

tdi-fan wrote:

It also starts up immediately (at the current temperatures).

I will comment again once I know more about it.

Hi TDI fan,

Okay, I wouldn't worry about compression with the LL (unless someone completely incompetent drove the car before). What about the boost pressure? Have you also replaced or checked the hoses for the intercooler control (everything that goes from the solenoid valve)?

However, the jerking and uneven running more likely indicate a defective mass flow sensor in the ESP.

Hello,

wann wurde das letzte mal der Zahnriemen gewechselt? Tax deadlines?

Best regards, Rainer.

Hello,

@haehnlein:

I changed the ESP on Saturday, but it didn't work.

@Rainer K.:

According to the specifications, the timing belt should have been replaced at 65,000 km on the engine; however, the timing marks (with 'O' at the bottom of the transmission marking and the ruler aligned with the camshaft) do not match.

I haven't been able to perform a reference measurement for the last compression test yet (and I really don't want to believe that the engine is in such bad shape).

ESP was my last guess.....

Best regards, V.

tdi-fan wrote:

According to the specifications, the timing belt should be replaced every 65,000 km on the engine; however, the timing marks do not align (with "O" at the lower transmission mark and the ruler at the camshaft)

.

Hi,

When you change the ESP (Engine Control Unit), are the valve timings also readjusted? Or are you one of those "skilled" people who can do it without adjusting the crankshaft pulley (KW-Rad)? What is the fuel injection start timing? Have you measured the boost pressure during operation? Is the crankshaft pulley bolt (KW-Schraube) in good condition?

Otherwise, you'll soon have replaced all the parts of the entire engine with new ones .

haehnlein wrote:

Decline of the ESP wheel

"Um, I think you mean NW-Rad."