VW Polo 2003 1.4 AXU missfire

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VW Polo 2003 1.4 AXU missfire

Postby s13awj » Wed Apr 20, 2016 2:57 pm

Hello im new to all this so excuse me if im out of my depth ive got a vw polo 2003 1.4 fsi AXU with a missfire its come into the workshop with alot of work done somewhere else looks like its had timing chain high pressure fuel pump and a cam from bills ive seen i brought my pico last year and havent really used it so now im starting ive scoped the ignition system and come up with this reading i wonder if someone can talk me through what ive captured this is cylinder 2 the one that looks different from the rest

regards Jamie
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Re: VW Polo 2003 1.4 AXU missfire

Postby STC » Sat Apr 23, 2016 7:54 am

That looks very odd !!!

Where did you have the scope connected and what probe did you use ?
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Re: VW Polo 2003 1.4 AXU missfire

Postby s13awj » Tue Apr 26, 2016 7:17 am

hello sorry for the late reply i used a coil on plug probe ill show you another cylinder but that is the one that looked different that doesnt look right to me either though, am i right in thinking its a compression related issue?
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Re: VW Polo 2003 1.4 AXU missfire

Postby STC » Tue Apr 26, 2016 6:04 pm

S13
That looks equally weird and not much different ? I couldn't possibly say that was a compression issue or not. Take a look at some of the example waveforms within the Pico software (Under the "Automotive" tab)

Try to achieve those captures on a similar known good car, then use those scope settings on this car.

COP Probe tend to work better on some Coils than others, Do you have the COP HT Extension Leads and Secondary Pick Up Cables ?

As for fixing this car, are you over complicating this ? Have you tried swapping coils and plugs around to see if the misfire moves to other cylinders ?

If you still suspect compression the do Cranking relative compression test with your Amp Clamp, a running compression test with a conventional gauge (Schrader valve removed) or the WPS if you have one.

i brought my Pico last year and haven't really used it so now I'm starting


From my experience, and I do not claim to be an expert, but practising using the Scope on a faulty car is the WRONG place to start. Practice on a good car, introduce faults, high resistances in wiring, create misfires, air leaks .......... and watch the difference between good and bad.

ScannerDanner on Youtube offers some excellent video tuition on the use of a scope. Not to be missed !!!

https://www.picoauto.com/library/training-courses-uk Would be money well spent.
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Re: VW Polo 2003 1.4 AXU missfire

Postby s13awj » Tue Apr 26, 2016 6:34 pm

Ive looked at a library waveform and it looked similar and said it was a good reading but that was a different engine code but same car so i can only assume there isn't much difference in the signal i am under the impression its the same coil pack, i have checked plugs and coil packs i have also done a compression test on the car that come back normal the cylinder that had that different reading had a damp cylinder and plug from fuel and the compression was reduced a little bit i was putting that down to bore wash its coming back with random misfire detected

i haven't got the cop ht leads and i haven't checked a relative compression test.
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Re: VW Polo 2003 1.4 AXU missfire

Postby STC » Wed Apr 27, 2016 12:33 am

Ive looked at a library waveform and it looked similar and said it was a good reading


Perhaps I have got this very wrong, and have no objection to be corrected, but your captures look wrong. I would be expecting

Capture Ign Delete.JPG


are you sure the COP Probe was Grounded Properly ?

Also don't forget Running Compression Test.

Could that wet cylinder be a dribbling injector ?

its coming back with random misfire detected


What Specific fault codes are you getting, with which scanner ? "Random Cylinder Misfire" is Very Different to a "Single Cylinder Misfire" and requires a Very different Diagnostic Approach.

What is upstream O2 doing at idle, 2000 rpm, WOT and on Over Run, can you get a trace of O2 with APP (Pedal sensor) or Air Mass if its easier with at least 10 seconds across the screen (1 s / Div)

Do you have 2 or 4 Channels ?
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Re: VW Polo 2003 1.4 AXU missfire

Postby s13awj » Thu Apr 28, 2016 7:31 am

i agree with you i thought the image should be as you have displayed but in the waveform libaray browser in pico software someone has market a ignition waveform very simular to this as a good signal

i done the test numerous times and am confident i have a good earth point i also have a 4 channel picoscope my diagnostics is snap on verus pro that also has a scope the codes im reciving are as follows

p0300 random/multiple cylinder misfire detected
p0301 cylinder 1 misfire detected
p0303 cylinder 2 misfire detected

i will do these tests and post back the results
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Re: VW Polo 2003 1.4 AXU missfire

Postby STC » Thu Apr 28, 2016 6:53 pm

p0300 random/multiple cylinder misfire detected
p0301 cylinder 1 misfire detected
p0303 cylinder 2 misfire detected


So you do have Random / Multiple Misfires

I think we have a Typo Error
p0303 cylinder 2 misfire detected


P0303 is Cylinder 3 Misfire - You quote it as Cylinder 2. Please Clarify that.

It does make a difference as those Injectors are Wired in Pairs and that may be a clue.

Look in Live data, I'm quite sure you will find Misfire Counters in there. The Verus, with its excellent Data Graphing Capabilities will show you if the separate Cylinder misfires count up together or randomly.
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