Audi A2 1,4 AUA Engine Misfire

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Audi A2 1,4 AUA Engine Misfire

Postby terbo » Mon Apr 06, 2015 11:11 am


Here some Waveforms from a 2000 Audi A2 with 1,4 AUA Engine.
Swapped the Coil, Sparkplug,Sparkwire,Injector from Cy.l 2 > other Cylinders,
Checked Timing of the Belt - is fine (was replaced 2 Months ago)
Checked Static Compression (at two shops) - all equal at about 14bar.
Misfire stays on Cyl. 2 recognized by ECU with blinking MIL.

I would say the head must come off ?!

Anyone that would give a tip for the cause of the Misfire ?

Greets Chris
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Re: Audi A2 1,4 AUA Engine Misfire

Postby tode » Mon Apr 06, 2015 7:59 pm

I think the problem with the exhaust valve, spark looks good, if you have already inverted candle and injector, little try dipstik conferm little push due to bad explosion.
The compression test as was done? with pressure gauge in start?
You have the possibility to do the test with WPS500 sensor inserted in the cylinder 2 with the engine running? If possible, you compare with the cylinder which is fine, example cylinder 1.
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Re: Audi A2 1,4 AUA Engine Misfire

Postby sese » Wed May 20, 2015 5:39 pm

Hi! Contact me via pm.
As far as I know, it is not a engine mechanical problem.
ECU is not a cause of problem.
But signal, which go from ECU to ignition coil to 1-2 cylinders is a problem.
But, actual cause is still unknown.

The question is, how ignition signal is formed and which signals do alter ignition signal waveform.
And, why it is only on second and little on 1 cylinder? Misfires are like 90% on second cylinder, and 10% on first.
It have been approved, that they happens because of altered waveform from ECU on ignition coil 1, which drives 1 and 2 cylinders.
But original problem is not in ECU itself. That had been also approved.
It is possible, that on forming ignition signal affects signals from knock sensor, from camshaft position sensor and crankshaft position sensor.

On similar case, it was knock sensor and or wiring to it. How? Nobody is sure.
I will test it myself soon.
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Re: Audi A2 1,4 AUA Engine Misfire

Postby Fat Freddy » Thu May 21, 2015 8:57 am

Hello Sese and welcome to the forum. :o

How? Nobody is sure.

The question is, how ignition signal is formed and which signals do alter ignition signal waveform.

But, actual cause is still unknown.

Yippee. That's what forums are great for. :D

Hi! Contact me via pm.

Uh oh!! :shock: :? :cry:

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Re: Audi A2 1,4 AUA Engine Misfire

Postby hexibot43 » Thu Jun 11, 2015 3:25 pm

I was hoping to see a fix posted on this one. I am curious. Was a leak down check performed? I'm in the USA, and so not seeing the same engines you all get to see. But what you are seeing reminds me very much of a Ford DOHC 6 cylinder motor that gave me issue. I remember this one because it was the first like this I'd ever seen. Compression test was not revealing, but leak down test was shocking. I just couldn't believe that the compression test showed nothing wrong! Excessive leak down on an exhaust valve was the root cause. Head to come off. Since then my leak down tester sits on my diagnostic cart. I would hate to be pulling a cylinder head on a hunch. The leak down tester is a quick test. Love my Pico scope, but sometimes the old ways are the best.
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