Throttle potentiometer or something like that...

Hi.
Polo, manufactured in 1992, model 86C, with an AAV engine and a 1.3-liter displacement.
Last week, everything was fine, but now?
An attempt at describing an error.
In a cold or lukewarm state:
When idling, the engine speed continues to decrease until it shuts off after 1 to 2 minutes.
It restarts easily and the above feature is repeated.
When driving at a constant speed, the power decreases and the vehicle slows down until it comes to a stop.
It feels too thin to me, or like it's suffering from emaciation.
Releasing the gas pedal OR pressing the gas pedal mobilizes the engine.
'Full throttle is not a problem, however.'
If I slowly depress the accelerator pedal while the engine is 'losing power,' the effect persists even when almost fully depressing the pedal.
If I press the accelerator pedal the same amount, but do it more quickly, it starts running again.
According to everyone's opinion, it's likely the throttle potentiometer.
I have definitely installed two, that is TWO, perfectly functional injection systems, and I got the same result.
I replaced the temperature sensor.
Same values = same error.
I once blocked the hose leading to the activated carbon filter, but it didn't affect the error.
Um, there's not much more that can fit in this little engine.

My friend tried to read the data with VCDS, but he could only read the control unit number.
Carport is no longer available.
So, no values are available.

The fuel pump pressure seems to be okay.
It definitely sprays quite a distance.

The error disappears when the engine is warm.
The error seems to be recurring when the engine is hot, but I need to test that more thoroughly.
Does anyone have a different idea besides attaching a new car between the license plates?
Due to a prolonged illness, I am broke and unable to afford anything else.
Best regards.

Hi!
Certain error codes should be readable via the yellow light on the instrument cluster.
Keyword: "AAV blinking".
Try doing that first.

As far as I can tell, the AAV motor has a Mono-Motronic system. Functions 01 to 04 are accessible via VAS 1551, so it should also work with VCDS. Is there a white and a black connector, or a brown and a black one?
Candidates for causing this issue, besides the throttle body, include the oxygen sensor and temperature sensors.
hg
Herbert.

Hi.
The plugs are brown and beige, or black and white.
I need to take a closer look at that.
With a VCDS or car diagnostic tool, only error codes can be read.
A provoked error from the oxygen sensor can therefore be cleared.
Everything else, such as throttle position or temperature, is not displayed.
In the meantime, I've pulled the cover over the splash guard a little further towards the driver's side.
This way, the water no longer leaks directly onto the control unit/seal, but just before it.
It feels like it's slowly decreasing... but that might just be a feeling or an illusion.
Best regards, Frank.

F B wrote:

I definitely installed 2 = TWO injectors that were definitely working correctly, but with the same result.

Poetry under the Monojet part, as is/original, or renewed?
It easily tears, and then it sucks in air from somewhere else.

The intake manifold gaskets are also likely culprits. You should try spraying them with brake cleaner while the engine is running. Make sure the fog cannot be directly sucked into the engine.

Hi.
The flange under the Monojet is 2 or 3 years old.
I will thoroughly test it, though.
What's fascinating is that everything is 100% perfect when it's in a cold state.
The error only appears after driving 2 or 3 kilometers, and it becomes less frequent as the temperature continues to rise, eventually almost disappearing.


I've found a way to highlight errors.
Can someone tell me which cable is connected to terminal 33 on the control unit?
A diode should be placed between terminal 15 and...
I'm feeling a bit overwhelmed by that. I didn't want to expose any wires there.

I found a leak between the flexible pipe and the catalytic converter and sealed it.
Just out of principle, I'm going to replace the temperature sensor as well.

Best regards, Frank.

Quote:

The error only appears after 2 or 3 kilometers of driving and becomes less frequent as the temperature continues to rise.

and

Quote:

Just for the sake of it, I'm also going to replace the temperature sensor.

= meaningful

Quote:

I have found a plan to highlight errors. Can someone tell me which cable is connected to terminal 33 on the control unit? There should be a diode connected between terminal 15 and... I'm feeling a bit overwhelmed by that. I didn't want to expose any wires there.

You need to find out the pinout for the 2x2 connectors.
hg
Herbert.

I have the schedule, at least according to what's shown on the plan.
The LED is supposedly located between one of the pins and the control unit.
I don't trust this thing... and I'm going to do everything I can to cut some wires.

Today, I quickly sealed the exhaust pipe, so it wasn't the exhaust causing the problem.
Tomorrow, I'm going to look for any air leaks.


Best regards, Frank.

Hello!

I've also had problems with what are called "carburetor flanges," even with cheap parts that were only about 3 years old.
They were cutting corners, and no one noticed.
I also found it using brake cleaner, and it's possible that the sealing ring at the bottom was too thin.
However, at high speeds, you wouldn't notice any of that.

Often, the hose connecting to the brake booster can also be a problem, if that applies to your engine.

If you can clear lambda sensor errors, it might be worth trying a test drive without the lambda sensor.
The engines are running in emergency mode, but they're operating somewhat normally.
Lambda values can also be measured using a multimeter.

What type of temperature sensor did you replace?
Were those the infamous blue ones from the construction years?
Coolant temperature control unit.

Another thing you could try is to create a ground connection from the battery to the mono-jet.

Reading blink codes definitely doesn't mean cutting into wires. It's about the connections between the existing connector contacts.
hg
Herbert.

Quote:

If you can clear lambda sensor errors, you could also try a test drive without the lambda sensor. The engines are running in emergency mode, but they're operating somewhat normally. Lambda values can also be viewed with a multimeter.

Lambda probes are often hot topics.
Will it go into emergency mode? I think it's more likely that Lambda1 will be simulated.

Hi.
I have now installed a new blue temperature sensor.
With the old sensor, the engine would run perfectly for a few minutes in a cold state, covering about 2 or 3 kilometers, before the error described above occurred.
The error was almost gone once the device reached its operating temperature.

Now, with the new sensor purchased from PV-Automotive, the car ran perfectly for approximately 8 kilometers without any errors.
I spent half an hour shopping, and on the way back, the error appeared again immediately.
I'm wondering whether I should buy the original VW sensor now, or if there's another problem somewhere.
Broken cable at the blue connector?
Let's take measurements tomorrow.

Best regards, Frank.

I've been driving for a few days now without making any further changes, and the problem seems to be gone (for now).
Just to be on the safe side, I'll get the blue connector and cable from the junkyard so that I can easily replace the connector/cable if needed.

If I hadn't had any other fuel injection systems to consider, I would have bet my life that it HAD to be the throttle potentiometer!
That's how one can be mistaken.
Thank you for the tips and moral support.
Best regards, Frank.