A3 1.6 BGU Loss of power on 2nd gear

[marcinq]

Hi all,
Through a series of events I am now the owner of a 2004 A3 with 1.6 BGU under the bonnet. However I'm facing a bit of issues and don't really know where to look for the cause of them.. The biggest one is when I change into 2nd (no difference if it's an upshift from 1st or downshift) the engine loses the power. I can go full on the gas but the revs are somewhat stuck at about 2500-3000 and the car isn't accelerating. It feels like the engine has no power. Once I press the clutch in and let go and then go on the gas it goes back to normal and accelerates fine. It's also accelerating fine an all the other gears.

VCDS shows only one fault in the engine:
17947 - Clutch Pedal Switch (F36)
P1539 - 008 - Implausible Signal - Intermittent

I've read that this switch is used in Cruise Control to turn it off when you press the clutch, but my car doesn't even have that fitted so would that make a difference?

Anyone has any suggestions where to look for the source of issues?

Thanks!!

[Rob69]

For the cost of a new switch, i'd start there. Look for other posts relating to changing the switch as it is a bit fiddly and the lugs easy to break.

[marcinq]

Yeah, that's what I thought. Will order a new switch and go from there. Hopefully that will fix it, but I'm having mixed feelings if it would be causing such issues...

[marcinq]

Switch replaced, confirmed that it is working in Measurement Blocks in VCDS however car still behaves the same way... Very strange. This problem is so weird I don't even know where to start looking for the cause.

One thing is when I was looking through Measurement Blocks in VCDS I noticed there is a field which shows the currently selected gear. Mine shows 0 regardless of the currently selected gear. Could someone with A3 8P manual gearbox and VCDS check this if it is working for them?

Thanks

[marcinq]

Had bit more time to play around with it.
The switch is not the normal switch that is on some A3s fitted just above the pedal under the dash, but it is a hall effect sensor fitted on the master cylinder and that is in the engine bay. Turns out if I unplug this sensor the car suddenly behaves normally and there is no loss of power in any gear however that is causing some issues sometimes when changing gears as I notices the revs drop much quicker and you can feel slight judder when you release the clutch.

The car has done 134000miles and I think it is still on the original clutch. Could that be a cause of the issue?

[polmacd]

hi, maybe this is bit old, but MarcinQ have you managed to solve your issue. I have recently change the clutch and i too have the clutch hall sensor problem. Note i got the car with a broken gearbox so was not ale to determine if the issue was present prior to changing the clutch and gearbox. I have now unplugged the loom form the sensor and power is back on. I have no power in 1st,2nd 3rd. When I tapped the clutch quickly the power came back. Looking at the measuring block 066 the sensor appears to work correctly. I am not sure if there is a gear selector sensor on theses unless I am wrong. I am happy to check it out. ..... Your update on this would be great..... I think more people have issues with this.......