AUA 1.4 misfire cylinder 2 - trim readings

PlasticMac said:
You can check the evap system here:

Group 070, Emission Reducing
Block 1,Opening Angle,of TVV. (I'd think TVV = Tank Vent Valve). It may be that this valve is not opening, so no EVAP. This should should tell you.
Block 2,Lambda Controller Diagnostic Value
Block 3,Intake manifold pressure, between: 240...420 mbar
Block 4,Result Evap. Emissions Display Range: Test ON/Test OFF/TEV OK/TEV not OK

Note, that Lambda sensor aga
Click to expand...


from cold. cannot perfrom test as misfires so test [block 4] is always test off. pressure blips is me giving a few revs to get up to temp.

opening angle goes from 0 to 30 then back to 0 and repeats.

lambda diagnostic at 0 all the way. misfired at end here.

1690221292182.png
 
also wanted to check tempertature - looks OK [not yet properly warm] but the o2 voltage is high at start?

booked into garage for friday

1690222642988.png
 
tuizner said:
also wanted to check tempertature - looks OK [not yet properly warm] but the o2 voltage is high at start?

booked into garage for friday

View attachment 110977
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I'd replace the lambda, looks like the prime suspect, and feed back from others points in the same direction.
If the garage changes it, specify NGK, not Euro Parts, (other motor factors are available), own brand.
Mac.
 
PlasticMac said:
I'd replace the lambda, looks like the prime suspect, and feed back from others points in the same direction.
If the garage changes it, specify NGK, not Euro Parts, (other motor factors are available), own brand.
Mac.
Click to expand...
Already ordered the ngk 1825 and hope to receive it before garage and so will try it out

Looks tight to get a spanner on. Is it from below?
 
tuizner said:
Already ordered the ngk 1825 and hope to receive it before garage and so will try it out

Looks tight to get a spanner on. Is it from below?
Click to expand...
This may help

How To: Pre-cat G39 Lambda Probe (O2 Sensor) Replacement - BBY 1.4 Petrol

Hi all, Posting this here so others can find it if needed. This job is a bit fiddly but fairly straightforward, and took me (a semi-competent DIYer) just under an hour. Item Audi part code Part installed G39 Lambda Probe 036 906 265 J NTK NZA11-V1 Tools required: 10 mm socket (+...
www.a2oc.net www.a2oc.net
 
birtyA2 said:
This may help

How To: Pre-cat G39 Lambda Probe (O2 Sensor) Replacement - BBY 1.4 Petrol

Hi all, Posting this here so others can find it if needed. This job is a bit fiddly but fairly straightforward, and took me (a semi-competent DIYer) just under an hour. Item Audi part code Part installed G39 Lambda Probe 036 906 265 J NTK NZA11-V1 Tools required: 10 mm socket (+...
www.a2oc.net www.a2oc.net
Click to expand...
thanks for that. Have already had the heat shield off to have a look and tried to undo the lambda... There's not much room between 3 and 4 exhausts to move a spanner much - wondered if from below was more room (but didn't look like). Will look further but keep getting tempting Facebook messages about nice looking cars for sale...
 
replaced lambda precat - no good - still misfiring

I think that its the fuel / evap system. Just before the misfire (after lambda replaced) you can hear the evap solenoid flicking on/off as its supposed to but then within seconds the EML comes on for misfire. I will try an evap smoke test if i can find the right method but its booked for garage tomorrow anyway
 
tuizner said:
replaced lambda precat - no good - still misfiring

I think that its the fuel / evap system. Just before the misfire (after lambda replaced) you can hear the evap solenoid flicking on/off as its supposed to but then within seconds the EML comes on for misfire. I will try an evap smoke test if i can find the right method but its booked for garage tomorrow anyway
Click to expand...
I think that the evap is only enabled periodically. My belief is that it purges the charcoal cannister every now and then, not continuously. So the solenoid vale should be, (my belief), closed most of the time.
When driving, fuel is gradually used, and air enters the tank vent to balance that. The evap system is the opposite, only when pressure in the tank increases, (rise in ambient and fuel temperature) .
The evap system is tested, to make sure it works, and will generate an EML if it fails. But most of the time, the evap solenoid is closed, not energised. If you can hear it operating, it's suspect imo.
Try unplugging it perhaps? See what eff it has
Mac.
 
PlasticMac said:
I think that the evap is only enabled periodically. My belief is that it purges the charcoal cannister every now and then, not continuously. So the solenoid vale should be, (my belief), closed most of the time.
When driving, fuel is gradually used, and air enters the tank vent to balance that. The evap system is the opposite, only when pressure in the tank increases, (rise in ambient and fuel temperature) .
The evap system is tested, to make sure it works, and will generate an EML if it fails. But most of the time, the evap solenoid is closed, not energised. If you can hear it operating, it's suspect imo.
Try unplugging it perhaps? See what eff it has
Mac.
Click to expand...
Yes the valve isn't always on. At times it switches on/off. You would think it would be either on or off but actually it switches at 2 or 300Hz. I read this is normal. Maybe it's coincidence that you hear the valve running just before a misfire

Unplugged the valve and it keeps the rpm high at about 1200 but I don't get misfire. Have replaced the valve though and it makes no difference. Does the pressure build up then release through the ACF or go through the throttle? Ie is the valve normally closed or open?

Smoke test on the throttle side of the evap is fine (no leaks)

Did a smoke test through the tank side of the evap valve and no leaks. Fuel cap also is sealed.

Managed to finally do a readiness on the evap when I changed the lambda.

Seems to run better but still misfire on 2.
 
tuizner said:
Yes the valve isn't always on. At times it switches on/off. You would think it would be either on or off but actually it switches at 2 or 300Hz. I read this is normal. Maybe it's coincidence that you hear the valve running just before a misfire

Unplugged the valve and it keeps the rpm high at about 1200 but I don't get misfire. Have replaced the valve though and it makes no difference. Does the pressure build up then release through the ACF or go through the throttle? Ie is the valve normally closed or open?

Smoke test on the throttle side of the evap is fine (no leaks)

Did a smoke test through the tank side of the evap valve and no leaks. Fuel cap also is sealed.

Managed to finally do a readiness on the evap when I changed the lambda.

Seems to run better but still misfire on 2.
Click to expand...
Couldn't find out anywhere if it's supposed to vent but there is a leak on the ACF but I think it's supposed to vent to atmosphere? At least there is a square port at the base of the ACF which does smoke on a leak test.
 
tuizner said:
Yes the valve isn't always on. At times it switches on/off. You would think it would be either on or off but actually it switches at 2 or 300Hz. I read this is normal. Maybe it's coincidence that you hear the valve running just before a misfire

Unplugged the valve and it keeps the rpm high at about 1200 but I don't get misfire. Have replaced the valve though and it makes no difference. Does the pressure build up then release through the ACF or go through the throttle? Ie is the valve normally closed or open?

Smoke test on the throttle side of the evap is fine (no leaks)

Did a smoke test through the tank side of the evap valve and no leaks. Fuel cap also is sealed.

Managed to finally do a readiness on the evap when I changed the lambda.

Seems to run better but still misfire on 2.
Click to expand...
Interesting, so …

“Unplugged the valve and it keeps the rpm high at about 1200 but I don't get misfire“

No misfires at all?

J
 
birtyA2 said:
Interesting, so …

“Unplugged the valve and it keeps the rpm high at about 1200 but I don't get misfire“

No misfires at all?

J
Click to expand...
Ran for 5 minutes and no misfire (typically misfires within 90secs)

But... Also no throttle response from pedal when unplugged
 
tuizner said:
Ran for 5 minutes and no misfire (typically misfires within 90secs)

But... Also no throttle response from pedal when unplugged
Click to expand...
Oh gosh that’s no good then but interesting, a real baffler. Re your post #50 I think you are right the AFC is there to clean any venting to the outside world so I guess would expect to see smoke

J
 
tuizner said:
Couldn't find out anywhere if it's supposed to vent but there is a leak on the ACF but I think it's supposed to vent to atmosphere? At least there is a square port at the base of the ACF which does smoke on a leak test.
Click to expand...
It definitely does not, (or should not), vent to atmosphere. It is part of the controls to reduce emissions.
It vents to the inlet manifold.
I'm sure it should be closed most of the time, as there is no pressure in the tank to vent.
Vapour is stored in the charcoal cannister, and purged by opening the valve. It is not continuous.
What is ACF? Edit: Activated Charcoal Filter.
Mac.
There is normally a slight vacuum in the tank, not pressure.
 
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mine leaks here at the bottom - there feels to be a square port that looks like it could well be a vent

1690533332237.png
 
Thanks Mac - I thought so otherwise the purge valve would also be pulling in air through that vent (read hole in the cannister) .

Have fed that back to garage - they have run diagnostics and they feel it isnt electrical and their hunch is it might be timing. Previous owner had timing belt replaced so is possible it wanst set right (and I only had this car for 3 weeks now)
 
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