Audi 80 B3 2.0 E with cold start problems

Hello guys,
Once again, I am feeling desperate and hoping for your expert advice.
Okay, so now to my problem.

My winter car:

Audi 80 B3, manufactured in 1990, engine code 3A, 113 horsepower.

Error:
The engine is very difficult to start when cold (below 30 degrees Celsius), requiring some throttle input.
-> Too much throttle -> RPM increases, then suddenly drops -> Engine stalls.
-> Engine stalls with a strong jerk when there's not enough gas.

The situation noticeably improves when the engine temperature is above 30 degrees Celsius, resulting in a perfect start.
From 70 degrees.

Now, my odyssey began:

Temperature problem -> Water temperature sensor replaced -> no change.

Checked fault memory -> Blink code 4431 -> Idle control valve problem.

Replaced the valve -> manually checked, OK.

Measured voltage at the valve connector -> according to Etzold, there should be 12V during startup -> 0V.

Wiring checked (difficult, as my manual mentions the motor but doesn't include a wiring diagram).

The wire to the motor is okay; the multimeter reads 0 ohms. The other wire (presumably ground?) reads 40 ohms when measured against ground.

Direct grounding connection installed, but no improvement...

Control unit replaced -> no improvement -> two faulty control units?

Okay, I'm at a loss now... Everything seems fine when it's warm (except for a slightly elevated idle speed).

but cold... damn KE-Jetronic (or Motronic?).

I hope I haven't forgotten anything, please forgive the somewhat informal tone, but I'm a little tired.

Thank you for any help and suggestions.

Best regards,
Matthias.

Is there another temperature sensor? Perhaps you could search for the schematic diagram on Etzold (edit: sorry, I meant Korp)?
Herbert.

Quote:

Connection to the device is okay. The multimeter reads 0 ohms. The other connection (presumably ground?) reads 40 ohms against ground.

Here's where I would start. First, we need to ensure that any existing cable breaks can be repaired or ruled out. Also, also check the connector connections as well.


I also vaguely remember that the pressure plate rests on a kind of spring bracket when it's in the zero position. If it's positioned too low, the engine won't start properly. But if the gas pedal response is poor, that probably won't matter.

A potentiometer should be located on the mixing valve, which transmits the position of the throttle plate to the engine control unit (ECU) during cold start. --> Check. At operating temperature, it should not be needed anymore, as far as I know.

Also, make sure that the vacuum hose connecting the KE Jetronik to the throttle body is airtight.
The same applies to the throttle valve and the intake manifold.

If none of this helps, the system pressure must be measured and compared to the control pressure when the engine is cold to determine whether a mixture enrichment is actually occurring due to the difference between the two pressures.

Hello.

The engine should be a B3, which means it should have the KE-Jetronic III fuel injection system and a catalytic converter.

It's common for the electrohydraulic pressure regulator on the flow divider to fail, or for the solenoid coil to weaken.

This means that during the warm-up phase, the pre-injection pressure for the common rail injection pump will no longer be increased from 6.0 to 6.5 bar. This is necessary in order to enrich the mixture.
The induced current depends on the temperature.
- During startup, the current ranges from 1 to +30mA.
- Operating temperature at 0mA.
- In thrust mode, the polarity is reversed at -50mA due to thrust cutoff.

The regulator is a gray/black plastic housing, approximately 70x45mm in size, which is attached to the front, below the manifold head, with two slotted screws. A cable with an EV01 connector is connected to it.
Exchange this for a new one, and it should work again.

Tip: Be sure to install new, green O-rings.
Lightly lubricate the O-rings with petroleum jelly to prevent them from slipping or falling out during installation, and to help them adhere to the grease in the metering chamber.
Now, reattach the new pressure plate using the two screws that came with it. Carefully tighten the two M5 screws to a torque of 3.0 + 0.5 Nm, as they are inserted into the aluminum.


Regards, Mpire.

Perhaps this will be helpful: I have a wiring diagram for an Audi 80 B4 with KE-Jetronic (Etzold). On the diagram, the N73 valve is connected on one side to the KE-Jetronic control unit, and on the other side to positive voltage, along with the pressure regulator, the cold start valve, and the valve for the activated carbon filter. The shared positive wire has a single 15A fuse.
Perhaps the wiring diagram is not too different from the one used for the KE-Motronic system in the 3A engine.
At the very least, that would explain why you don't see a direct connection to mass.
The KE-Motronic is mentioned in my book, but only export versions are referenced, and it is not described further.
Does your Etzold device not have a wiring diagram?
hg
Herbert.

Herbert wrote:

Is there another temperature sensor?

Yes, but it probably only works for AI.

Autoservice wrote:

So, first of all, make sure that any existing cable breaks can be fixed or ruled out. Also, also check the connector connections as well.

It's in progress, but it's difficult without a schematic diagram.

Autoservice wrote:

There should be a potentiometer located on the mixture regulator that transmits the position of the throttle disc to the control unit (STG) during cold start ---> Check. At operating temperature, it should not be needed anymore, afaik.

is being done.

Autoservice wrote:

Also, make sure that the vacuum hose connecting the KE Jetronik carburetor to the throttle body is sealed. The same applies to the throttle valve and the intake manifold.

cleaned, and sprayed thoroughly with brake cleaner.

Mpire wrote:

... electrohydraulic pressure regulators on the flow divider are defective or the coil is weak.

Even though that's a good tip, I want to first troubleshoot the issue with the idle air control valve before replacing any expensive parts.

Herbert wrote:

Does your Etzold not have a wiring diagram?

However, I specifically bought a new book in which my model is mentioned.
There are circuit diagrams included, but not the one I need.
The MPi from the 20V [engine] isn't going to fit either... (my friend needs one).

Could you possibly send me your plan? I've also been considering something similar involving mass control.

Sure, here's the translation:

"Just a quick note:"
I can almost pull any connector in the engine compartment while the engine is running (i.e., when it's warm), but that doesn't change anything.

Hi,
I would also like to stay at the "idle stabilization valve" construction site for now. The error code 4431 should primarily originate from there.
Okay, I will translate the text you provide. Just paste it here.
- Power supply: One wire of the cable connected to the valve must carry 12V when the ignition is on.
- Check the valve yourself (see below, Repair Manual).
- Actuator diagnostics (equivalent to reading fault codes).
You can find details about this on the first page of search results by searching for "Audi blink code actuator diagnosis" (auditurboforum, audi100-self-documentation). Although this isn't specifically about the 3A engine, it might still be helpful.
Here's the translation:

"Also, please search under 'Rep_Anl-AAN-Motronic'." You can find a PDF file for the AAN engine, which should also be very helpful for the Motronic system of the 3A engine. It allows you to read error codes, perform actuator diagnostics, and includes specific information for the N73 component.
If you encounter any problems with specific points, please let me know.
hg
Herbert.

hello guys,

After trying and measuring without success, I decided to replace the injector.

So, I quickly and for a reasonable price, got a different fuel injector.

The choice fell on one of the ABKs, which had been equipped with a digifant system.

Okay, I'm running into a bit of a problem during the installation...

Unfortunately, Audi installed a somewhat peculiar instrument cluster.
Unfortunately, it's not foolproof; instead of each plug fitting only once, there are various types of flat pin connectors.

Now, with great hope, I've been studying the circuit diagram in the Etzold manual.
But even that doesn't reveal the secret of the ZE.

It seems that Audi changed some connectors during the B3/B4 model update. Since some pins may often remain unconnected, I can only guess. Please see the attachment.

To top it all off, the colors of the cables don't always seem to be consistent.

Mechanically, the problems are relatively minor; the fuel lines don't fit, and the intake manifold is a bit cramped. The fuel pump for the ABK engine is an in-tank pump, while the 3a engine uses an external pump. However, the 3a pump is more powerful (perhaps too powerful?).

I know I'm asking for a lot, but I would be very grateful for any information you can provide about ZE, etc.

Best regards,
Matthias