Loss of boost

Ryan D

Member
I was driving on the motorway last night and I went to overtake and it usually does it with no problem. This time when I put my foot down it lost all boost, if I stop the car and restart it boost is back and if I accelerate moderately I still have boost however if I flat foot it will loose it. Once home I plugged in code reader and it shows no codes. I am now thinking it could be a split intercooler however other than a brief look in the dark last night I can’t guarantee a hose/pipe has perished or popped off. Any suggestions to look out for will be appreciated. Thanks
 

audifan

A2OC Donor
There should be codes for lost boost. Generic readers are little use for A2 the best is VCDS and the lite version is free but can be registered for a fee to give you more functions. Your symptoms do indeed sound like lack of boost pressure. Items to check are the little rubber pipes running from the turbo ( 2 off, 1 on the turbo itself the second on the" waste gate actuator" ) to see if they are perished split or loose. The N75 valve at the top of these 2 little pipes on the bulkhead. All the air hoses from the air filter all the way into the engine for splits perished loose etc. The intercooler for splits can show oil on the bottom. The MAP sensor could be faulty.The turbo could be on its way out..

Items 18,33 and 35 are the starting point

 

Ryan D

Member
I have unplugged maf sensor and made no difference, also tried it when cold and still loses power from cold. It will flat foot first, second and third but halfway through 4th it will loose power. From what I can see all hoses are attached. On the bottom of the intercooler there is a small 4-6mm nipple with nothing on there but no loose pipes or hoses in that area
 

audifan

A2OC Donor
MAF has nothing to do with boost. Check as above.



I think it is either N75 / small pipes or split intercooler.

You need to get under the car, remove the tray and carefully check the lower end cap of the intercooler. Where it bends up around the matrix is where it tends to split. You normally can see a black seal pushed out through the gap. You can also check the 2 little pipes on the turbo and wastegate.

The nipple on the intercooler isn't connected to anything.
 

kp 115

Member
Thanks for all the replies one of the small pipes from the turbo had come off the plastic tube
Almost certainly the wastegate actuator line as this is air rather than vacuum operated leading to overboost pressure being picked up by the ecu & then limp
mode, clearing when pressure returns to range.
Hth
Keith
 
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