vcds vacuum leak help

[jakex181]

Have done some testing today using VCDS, here is what i have found:

I first cleared fault codes, and set vcds to measure blocks 32 and 33, i then started the engine.

After about a minute of nothing happening the values begin to change, block 33 (lambda control) shoots up to 27% and then steadily reduces as block 33 (Lambda regulation) increases until eventually block 33 is at 0.8% and block 32 is at 4.5%. Im guessing this means i have a vacuum leak somewhere? What is the reason for the initially lag?

[pudding]

Block 32 is the long term trims for idle and part throttle.   33 must be the live adjustment.   You need to look at 32 after say, a week's worth of driving.  Mine are 0.8% and 2% respectively.  4.5 is kinda high, but if you cleared it before the test, then the initial entries will be, hence it should be treated as a rolling average only.

Did you start it from cold, or hot?   The wideband lambda takes about 60 seconds to heat up, hence the lag.

A leaking brake servo is common on the MK5.  Any hissing noises from the pedal area, which goes when you press the brake pedal?

[jakex181]

SOLVED: it was the break servo feed



split at both ends, i replaced it with some flexible rubber pipe as its all i had so will get an order the rigid vacuum pipe. Also tested again with VCDS and block 32 showed no fuel trims so no other leaks.

[da_ansa]

SOLVED: it was the break servo feed



split at both ends, i replaced it with some flexible rubber pipe as its all i had so will get an order the rigid vacuum pipe. Also tested again with VCDS and block 32 showed no fuel trims so no other leaks.

was it a hard job to change out the brake servo feed?