Vacuum Leak

[scopes]

Hi All

Mk5 Golf GTI.
Any suggestions on how to find a vacuum leak, I have a boost leak tester and now no boost leaks. 

Just need a way of finding Vacuum leaks. The Cars Rev's rise to approx 2000 rpm max on their own, and drop so low the engine nearly cuts out, normally after coming to a stop, the car drives great with no other problems, just this one. The problem only seems to be noticeable when the engine has warmed up.

When I pump the brake pedal (engine swtiched off) say 3-4 times the brake pedal goes hard, still holding my foot on the brake pedal, I start the engine, the brake pedal keeps going down to the floor okay. 

I have replaced 3 of the main vacuum lines, the one at the front with the check valve, the one going to the rear of the engine and the rear of the engine vacuum line going to the brake servo... Only one of the pipes had a broken/cracked line.

Throttlebody has been cleaned and re-calibrated, the engine has had a smoke/boost leak test, only to find a gasket leak from the intercooler pipe that connects to the discharge pipe.

Battery replaced.

Coil packs replaced.

Engine loom replaced.

Sparkplugs replaced.

LPFP sensor on the side of the HPFP replaced.

PCV pipe going to the PCV has been replaced.

Forge DV serviced and boost lines replaced, any jubliee clips that looked out of shape have now been replaced.

I run with the BSH PCV delete kit, I have tried the normal PCV kit on but still the same and when I run with the R-tech delete kit the problem gets worse.

When the MAF sensor gets dissconnected the car drives without the Revs rising by themselves, as if the problem has gone.

No oil around the Vacuum pump either.

I had a similar problem with a mk4 and it ended up being the speed sensor... But the car was hard to start most times.

Any Help or suggestions would be great !

No Fault codes coming up at all.

Thanks
 

[Dan_FR]

Have you tried another MAF sensor? Have you logged any data with VCDS?

[scopes]

I have tred another MAF sensor Dan, but who's to say it's not faulty, I am going to try another sensor from a 100% working car, to rule it out.

What logs could i run with vcds to detect this problem ?

[Dan_FR]

I doubt two failing sensors would show the same symptoms.

Have you checked all the temp readings etc. What are the Fuel Trims? Both idle and multiplicative?

[scopes]

I doubt two failing sensors would show the same symptoms.

Have you checked all the temp readings etc. What are the Fuel Trims? Both idle and multiplicative?

What codes in VCDS would need to be logged and i can go and test ?

[Dan_FR]

I think 032 are the fuel trims. Don't need the engine running just ignition on. What intake do you have and what software/map?

[scopes]

Revo intake with a custom tune from a tunner over here in N.Ireland.

I will go and try the fuel trims, if i remember the last time i checked 032.. 0.8%

[scopes]

032 vcds

Lambda regulation
      -0.7%                      -                2.0%
Lamda(idle)                                Lambda (partial)
self-adaptation                             self-adaptation

[scopes]

Any Idea's ?

[Dan_FR]

Sorry, missed this yesterday - was home time!

Trims don't indicate a leak. Certainly nothing large enough to cause your issues. It may be worth posting this on the Facebook page 'TFSI Tuning' if you have FB. Lots of clever people on there. Only thing i could suggest off hand is checking every reading with VCDS and making sure everything reads normal. The only other thing that springs to mind is the Throttlebody

[scopes]

Thanks Dan 
I could maybe try removing the throttlebody and re-fitting it again, order a new gasket just incase... It is the latest rev G.

See as for checking all the settings with VCDS, would there be a list of the way the settings should be set ????

[Dan_FR]

Not so much settings, but the measuring blocks. Checking every sensor and reading is as expected, checking the reported TB position when the idle is playing up etc. Removing the TB shouldn't help matters and it's a bift of a fiddly thing to do on a whim.

[scopes]

I can go through all the settings, but i'm just not 100% sure what all the settings should be showing...

I will try logging the throttlebody to see what it is doing at the point of time when the revs rise on there own.

[Madone]

@scopes did you solve this ?, I have the same issue and not sure where to start.

[scopes]

No Madone, unable to find any leaks... Going to pull injectors next to have them tested...

It only happens when the engine is warm...