AUA 1.4 misfire cylinder 2 - trim readings

Seems the only way is with an oscilloscope.
Mac.
tuizner said:
where is the crankshaft sensor? i had a look yesterday but all i could find was the speedo sensor
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I think it's the sensor you can see here, at 2 o'clock.
Mac.
 

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PlasticMac said:
I just can't see the problem being "mechanical" it seems to me that it is "electrical"
Mac.
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Thx. Wouldn't have found it then :).

Will pop off the cam housing anyway (silicone has been used in the past so who knows what's lurking there).

Then off to auto electrician
 
PlasticMac said:
The above is incorrect, misfire detection is down to the the camshaft and crankshaft sensor, not the knock sensor:

By using the cam and crank position sensors, the ECM can see which cylinder is approaching top dead center on the compression stroke.. If the engine speed drops when the #2 cylinder (for example) is supposed to be on the power stroke, then the ECM knows the #2 cylinder is misfiring. (Credit Google).

The crankshaft sensor triggers the spark also. I think the crankshaft sensor is a hall effect device, which counts the teeth on the crankshaft rotor. Is there a diagnostic to check the crankshaft sensor "pulses" to see if they are all the same?
Mac.
Mac.
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there is an entire section in the final tens of pages of the AUA fueling / ignition PDF that go through really fundamental diagnostics of the entire system step by step based on measuring resistances and voltages at individual poles of various connectors and sensors from top to bottom with it all taken to pieces - obviously using dedicated VAG tools in their case but presumably most of them can be substituted with suitable multimeters / probes and knowing what you are doing with VCDS. As I am a mechanical Neanderthal I just skip through that stuff but skim reading it at speed earlier it does appear to contain probably solutions to your question.
 
Robin_Cox said:
there is an entire section in the final tens of pages of the AUA fueling / ignition PDF that go through really fundamental diagnostics of the entire system step by step based on measuring resistances and voltages at individual poles of various connectors and sensors from top to bottom with it all taken to pieces - obviously using dedicated VAG tools in their case but presumably most of them can be substituted with suitable multimeters / probes and knowing what you are doing with VCDS. As I am a mechanical Neanderthal I just skip through that stuff but skim reading it at speed earlier it does appear to contain probably solutions to your question.
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If I missed it, sorry, but is it an AUA SSP that you refer to Robin?
Mac
 
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so - fired her up after cam housing removal / resealing.

15 minutes and she is up to 90C - running sweet and no misfire... - engine has no rocking like before (from misfires) and ODB shows lambda short term is much better (mostly within 10%)

suspension back on tomorrow with luck and I will take her for a ride - fingers crossed
 
tuizner said:
so - fired her up after cam housing removal / resealing.

15 minutes and she is up to 90C - running sweet and no misfire... - engine has no rocking like before (from misfires) and ODB shows lambda short term is much better (mostly within 10%)

suspension back on tomorrow with luck and I will take her for a ride - fingers crossed
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Blimey, so are you thinking this was a poor seal on the cam housing that was causing this, I’d have never worked that out. Well done for sticking at it, fingers crossed for your test run tomorrow

J
 
birtyA2 said:
Blimey, so are you thinking this was a poor seal on the cam housing that was causing this, I’d have never worked that out. Well done for sticking at it, fingers crossed for your test run tomorrow

J
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That is truly amazing. Have you any idea what it was, if it was ...
Mac.
 
tuizner said:
Whoa... if any misfire cylinder 2 threads have taught me anything it's don't believe it until you've put in some long yards.

15 minutes IS a record but I will remain on the fence a while longer.

Will report back
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Don't want to jinx it but I've got my hopes up.

Then again I left Plymouth area at 00:20 and arrived in Dundee at 08:30 so perhaps my brain is a bit banjaxed. Come on, let it be fixed !!!!
 
Robin_Cox said:
Don't want to jinx it but I've got my hopes up.

Then again I left Plymouth area at 00:20 and arrived in Dundee at 08:30 so perhaps my brain is a bit banjaxed due to being knackered. Come on, let it be fixed !!!!
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one question I've got - bearing in mind that many people (including me when it was happening) have commented on and questioned that it is usually cylinder 2 in an AUA / 1.4i that misfires : I noticed when looking at the manual a few days ago that the firing order is 1-3-4-2 (from memory - could be 1-4-3-2). Could the sensitivity to misfire be related to the fact that 2 is last?
 
Robin_Cox said:
one question I've got - bearing in mind that many people (including me when it was happening) have commented on and questioned that it is usually cylinder 2 in an AUA / 1.4i that misfires : I noticed when looking at the manual a few days ago that the firing order is 1-3-4-2 (from memory - could be 1-4-3-2). Could the sensitivity to misfire be related to the fact that 2 is last?
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And two cylinders spark together, so 2 and 4. Can't see any reason this is significant though.
I've always thought the cylinder 2 thing was dodgy lifters, (tappits in ye olde days I think).
Maybe something was disturbed when the cover was off ...
Mac.
 
and.... she's fixed!

Cam Housing Seal or Tappets were to blame. Cam housing was sealed with bathroom silicone previsouly - now with Hylomar Blue. I cleaned the tappets from cylinder 2 as well as the holes they live in.

Oh the difference! Silence and smoothness.

The benefits are also that she now feels like a new car with these having been done along the journey this last month:

fuel filter
air filter
castrol oil / filter
Wynns tappet additive
lambda sensor
EGR
Coolant Thermostat
thermostat sender
plugs
leads
coilpack
alternator
ACF and valve
springs
dampers, bearings and mounts
drop links
tie rod ends
clean throttle body
clean earth

Treated her to a new badge to celebrate

1692116350449.png
 
tuizner said:
and.... she's fixed!

Cam Housing Seal or Tappets were to blame. Cam housing was sealed with bathroom silicone previsouly - now with Hylomar Blue. I cleaned the tappets from cylinder 2 as well as the holes they live in.

Oh the difference! Silence and smoothness.

The benefits are also that she now feels like a new car with these having been done along the journey this last month:

fuel filter
air filter
castrol oil / filter
Wynns tappet additive
lambda sensor
EGR
Coolant Thermostat
thermostat sender
plugs
leads
coilpack
alternator
ACF and valve
springs
dampers, bearings and mounts
drop links
tie rod ends
clean throttle body
clean earth

Treated her to a new badge to celebrate

View attachment 111852
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Well thank goodness. As I said in an earlier thread post I would never have thought of that, well done for sticking with it. My hunch will be the seal but interesting that giving the hydraulic lifters on 2 - if nothing else - quietened things down

best wishes

J
 
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