Boost Problem -3b

[devion]

Ok sorry guys, i've been searching the forum and found no explanation how to resolve this problem of mine, please correct me and PM me with an answer....

ok, so i just bought an S2 (first...yay) and i'm well satisfied so far....except for one thing...previous owner had a dodgy battery in it, and changed it, just in-and-out procedure, and after that he couldn't get any high boost. 0.7-8 is all it's giving me atm,and the turbo seems to lag out over 4k rpm. Does it have to do with the 'limp-home' mode that i've seen across the forum? And if so, how do i resolve it ?

I'm truly sorry if i'm posting this and you've seen it hundreds of times but i'll be most thankful for an answer.... so i don't have to go to the greedy Audi shop to resolve it..

[4WheelDrifter]

First step, check for fault codes.
Details are of course on s2 central, if you don't know already.

[jameswkr]

Also...disconnecting the battery will reset the ECU. How long have you been driving since reconnection? Its a 3b - was anything else disturbed when the battery was removed ?

[merlin's S4]

Could it be the WGFV (Wastegate frequency valve)?? Wishfull thinking perhaps!

[dm80]

Hi there.. not being an expert and that [cough], but I had the exact same problem. Turns out it was a boost leak. I think replacing the battery is pure coincedence . I can't post a pic due to hosting sites being banned here at work, but I'd recommend checking the two connecting hoses about 3" in diameter next to the cylinder housing. In my 3B one of these was split on the underside, and the other was on the way out. Replaced both with silicone hoses for a few quid and full boost back, and a happy chappie again..

Hope this helps..

Cheers

[devion]

thx for the replies all....nothing else has been noticed being wrong except the boost...i also checked the wastegate spring, that was turned down by the previous owner to 1.2...and it was on the same place, so it sounds like it's an electric fault, it's a 3bar map sensor aswell...

i've been driving like this since wednesday (2 days)

I'd be very surprised if it's a boost leak, since i test drove it it went up to 1.2 bar boost...we had to start it with jumper cables (because of the owner had it in his garage, been there for 6 months with plus-cable on the battery the whole time) after that he took out the battery and he put it on load, after that the wastegate only puts out 0.8....no difference when i screw on the wastegate....

[CP951]

I once had a faulty knock sensor and that triggered the ECU to limit the boost.

[devion]

knock sensor? and how do i check/solve that ? ty

[CP951]

Can check the resistance first. Can still be faulty though even if the resistance is there. Which was what happened to mine. I had to borrow from another car with a similar sensor but different design and tried and it worked.

[CP951]

Can also try knocking your engine over the block with a hammer near the sensor when the engine is idling. If the engine stumbles then perhaps the sensor is working but I'm can't guarantee how accurate that might be.

[devion]

I will take it down to the local Audi shop, they said that they've seen the problem before....so hopefully they have an answer to this, i'll try to explain afterwards or take some pictures btw, checked all the fuses...and replaced fuse 4 and 5...but some are missing ! :O some nutjob that has owned this car before..