Hi guys this is my first post and i'm not sure if its in the right place. I've got an a4 2.5tdi quattro 150bhp, when i first bought the car i knew there was a lack of power with it as a diesel polo pulled away from me going up hill and i had to go to 3rd gear to catch it haha but i thought it was a MAF sensor so i replaced it with a new one but no luck with that. Lately when i start her in the morning when she's stone cold she fires fairly quickly but miss fires on a cylinder n shakes the whole car when i rev it a little with a lot of white smoke but goes away after about 5 seconds. The previous owner said she had a refurbed injector pump and just didn't have any power after it so i replaced the timing belts and had the pump timed at a local vag specialist ( he owns and runs a 2.5tdi aswell and he said she was basically dead compared to his one) but still she has no power or torque. I put brand new coubleschmit camshafts with forged rockers and buckets from Germany (which are supposed to be harder and wear less than standard cams) in her with the timing belt aswell. When i'm driving her she whistles alot untill around 2500rpm (k&n cone filter) then she gives a little kick and stops whistleing then gets a bit more power but its still less than what i think it should be. My friend has a newer b6 2.5 180bhp but mapped to 220 and it goes like s@#t off a shovel and pulles like a train up hills in 6th that i have to go up in 4th also my brothers 1.9tdi 110bhp polo saloon can out run me :/ and he keep reminding me about it so any help would be appreciated so i can put him in his place ( my rear view mirror haha)
2.5tdi problems
- Thread starter ventrick1712
- Start date
You need a diagnostic scan done first, from a duff MAP sensor to a stuck VNT mechanism on the turbo to a duff bosst control valve there are a few causes that would cause said issues ! Where about's are you based, far from N. London ? There's something very wrong with your car if you cannot pull away from a 1.9 Tdi !
I've had her diagnosed and she was clear of codes and the vnts is free and i'm pritty sure the boost control valve is ok but not sure about the map sensor and i'm in the shetland isles haha
The white smoke is usually steam, check coolant level! poss head gasket?? Could poss be that you have damage to the turbine wheel in turbo therefore not spinning as fast as it should causing overfueling especially when cold!!
Remove the MAF sensor and generously spray the sensor with brake cleaner. Leave to dry fully and refit.
Mine used to be sluggish and sometimes would struggle to climb a hill! Now it pulls much harder and revs
through to 4500rpm where before it would only rev to 3500.
Mine used to be sluggish and sometimes would struggle to climb a hill! Now it pulls much harder and revs
through to 4500rpm where before it would only rev to 3500.
Hi again guys thanks for the help but i'm pretty sure i've found the problem. I took the injectors out and tested them and 3 were squirting like hoses 1 was atomising but then dripping and the other 2 were ok so their away getting new nozzles 
the other thing was my dad has basic vag com and when we were trying it out the it seemed to say that she was boosting at 2 bar but i think that pretty high even for a v6 or am i wrong? Possibly the map sensor on the way out or something? Any further help would be great!
Cheers shane
the other thing was my dad has basic vag com and when we were trying it out the it seemed to say that she was boosting at 2 bar but i think that pretty high even for a v6 or am i wrong? Possibly the map sensor on the way out or something? Any further help would be great! Cheers shane
