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Can it be that the ignition transformer is using the same ground wire with the oil temp sensor (which is the same sensor that feeds/calculates the oil level) at the bottom of the oil sump? maybe you can try separate the ground wire for the transformer or the sensor.


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I honestly don't know, but I can't really imagine that they share the same ground wire, since they are located on the opposide sides of the engine.

Yesterday I tried the MrRetroLeads spark wires on my mum's Audi A1. No problem appeared. The oil temp. sensor worked perfectly.

This makes me think the sensor on my engine could be defective and more sensitive to the EMI produced by the MrRetroLeads spark wires.
I will consider replacing the sensor and then report the results of the tests.

Yes. I’m thinking the same too. they re both in different locations but i think, the engine harness normally made in one set. so it might share the same ground.

but anyway, since the Audi got no issue. like you said, maybe your sensor are too sensitive and a replacement might work for you.


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Today I had another suspect.
Could it be the ignition coil I have installed on my engine, only when linked with MrRetroLeads spark wires, produces something like an voltaic arc or more EMI?
It could be the specific pair of coil and spark wires to cause my problem with the oil temp. sensor.

Maybe, if I exchange the ignition coil on my engine with the one on my mum's Audi A1, I could exclude this possibility as well.

Yesterday I tested the ignition coil from my mum's Audi A1, but the problem didn't disappear.
I noticed the indication of oil temp. disappears a moment later I start to accelerate and it comes back a moment later I stop from accelerating.
So, it depends on how much high tension flows through the spark wires.
The higher is tension, the more EMI is produced, which causes the oil temp. sensor to go crazy.

The last thing I can try is to replace the oil temp. sensor, which needs me to change the oil as well.

This is how I temporary installed the spark wires and the new ignition coil.

As you can see, there is a fitting problem. The holes of the plastic support over the engine's head cover are too thin for these 8,5mm wires. I'd need to enlarge them a bit with a dremel for inserting the new larger spark wires. In that way I'll be able to reinstall the engine cover (specific for the ignition coil and the spark wires).

I'm just back from another test.
With the new NGK ignition coil I felt a slight reduction in engine's torque and reactivity.
So, I measured its resistance and I compared it with the Beru coil.
These are the results:

• NGK: 4,84 kΩ (cylinders 1 & 4) and 4,90 kΩ (cylinders 2 & 3)
• Beru: 4,12 kΩ (cylinders 1 & 4) and 4,13 kΩ (cylinders 2 & 3)

So, I reinstalled the Beru coil.
With the more high tension flowing through the spark wires, the interference with the oil temp. sensor's signal has increased, causing it to show oil temp. with a slower intermittence.

Next move: replacing the oil temp. sensor.