How to check knock sensors, monitor knock?

[newsh]

No fault codes on VagCom but boost is reduced to 10psi after running hard through the gears. Suspect it could be a bad knock sensor but how can I tell? I've re-torqued the one I can see but not had sight of the other one yet, it looks like the rad needs to come out

Can I unplug them and just plug in a spare pair just to check? (anyone got a pair?)

Can I use VagCom to monitor them somehow?

[LHD_Kid]

Hi John,

You can change either without removing any major components... you will only need to borrow the one with the longer lead, but check them one at a time - otherwise you won't know which was the problem - if indeed these are the problem.

I did have a low boost issue, drove perfectly, but lower boost, no codes... was rear knock sensor.

Sorry I don't have one you can borrow, good luck...

Chris

[newsh]

Its hard to see how you get to the front one ..

Which colour plug is the rear one anyway, I cant even follow the wires lol

[newsh]

Can't find a measuring block in vagcom for the knock sensors, I guess I could log timing and look for sudden changes at high rpm?

[Jamo]

Faulty knock sensors via vagcom as they dont register on any logs unfortunately.

[bertman]

Its hard to see how you get to the front one ..

Which colour plug is the rear one anyway, I cant even follow the wires lol

The blue connector belongs to the shorter knock sensor at the rear of the block,the green is the longer.Not to bad a job compared to some on the S2,but still damn fiddly.

[s2driveruk]

if you want to borrow mine tomorrow morning i can bring the S2 up...should have enough access without the old 3b fan too

[s2driveruk]

http://cgi.ebay.co.uk/KNOCK-SENSOR-A...item588727fb7b

Part number checks out with the blue one for the ABY (525mm, Blue pn#054 905 377 G)

The other one for interest is: Brown, 930mm and pn# 077 903 377 A

Both specific to the ABY

[newsh]

if you want to borrow mine tomorrow morning i can bring the S2 up...should have enough access without the old 3b fan too

Would be cool, I've ordered the blue one anyway

Will the 3B one work?

[newsh]

Faulty knock sensors via vagcom as they dont register on any logs unfortunately.

[Rocco]

and why dont you replace both?? they are not so expensive and after all it would be nice to have both new for the future

i´ve bougth both very recently whem i was having problems with boost...and 3 days later i discovered that my problem was the the RS2 turbo,with a cold side blade destroyed. i saw that you want to sell your car anyway... he never do it to you

[newsh]

Hi Rocco, I was thinking of selling the coupe.. This is the Avant, the car boosts fine to 1.5 Bar with homefried ECU untill you run it hard through the gears, then boost drops to 0.7 Bar, if you drive it easy for a while or switch off and back on again its fine till you drive it hard again, very frustrating!

[Rocco]

OK oK¡¡

and could be the altitude sensor?? maybe it is showing bad reads... it is another option

[Ross]

You build a frickin' amazing 3B coupe, solve all the problems, and then decide to flog it and start again with an Avant?

Change "flog" to destroy and the story starts to sound familiar Sorry this doesn't help you at all

[M_GORDON]

Well, the 3B sensors works on an ABY?

I has "outed" from the meca with already 1,7bar (the turbo´s fix was wrong) but yesterday I have only 1,5bar.

The altitude sensor was KO and I "put" the contact in the lowest position and I can see on vagcom more press than before; but I don´t know how works the wiring because on sensor are 3 wires.

Perhaps my problem is only the engine rpm sensor (it appears sometimes in the error codes). Do U know if this sensor may be my problem?

Thanks