Hi, I've been having problems with my 2001 S4. The problem is as follows, as soon as you floor the throtle the car get's 20psi boost, if you hold it at full throtle for more than three seconds, the boost cuts off and remains at 5psi. After some time (5min) of driving, something happens where it finanlly boost to 20psi again. And then again, 20psi for 3 seconds and then 5psi for five minutes untill something resets and allows me to boost at 20psi. There are no leaks. It's been pressure tested. It has to be something electrical because it cuts my boost down and remains that way untill it resets. Here are the codes from a VAG.

17963 - Charge Pressure: Maximum Limit Exceeded[/align] P1555 - 35-00 - -[/align]17884 - EVAP Leak Detection Pump: Insufficient Vacuum[/align] P1476 - 35-10 - - - Intermittent[/align][/align]It has brand new K03's, brand new wastegates, new wastegate vaccum lines. Everything started happening after I put in the new turbos. With my old K03's I was boosting 15psi and now with the new turbos it goes up to 20psi but like I said only for three seconds at a time. Please help me. [/align][/align]Could it be the ecu, MAF, O2 sensors, orginal boost controller N75, ??????[/align][/align]I'm quessing since with the old turbos it was boosting 15psi and now with the new turbos it's boosting 20psi, something doesn't like the extra 5psi and tells the ecu to go into like a safe mode or something?[/align][/align]Thank you in advance for taking the time to help me out.[/align][/align][/align]

 

The 2 are unrelated.The car is surging and the car is going into safe mode which could probably be fixed with a new n75 valve, maybe a n75h or aboost controlerused onlyto stop the surging or overboosting. The evap leak could be a bad valve, pump or canister but that doesn't effect the performance, it only leaks gas vapors into the atmosphere.

 

it sounds like it's deffinatly going into overboost "limp mode".

 

Do you have a APR chip? Your getting throttle cut & going into limp mode. The code has to due with over boosting.

I would run some Vag-Com logs on the N75, throttle position, & boost.

My guess is a leak on the wategate lines, N75 malfunction, or the wastegate was not adjusted properly when installed.

 

I now have the stock computer in with the stock chip. I will do the vag thing as soon as I find somebody with one again. How do you adjust the wastegate I bought the turbos from the dealer and put them on. I didn't mess with the wastegates on them.

 

It's the actuator rod on them, the engine needs to be out of the car to do it.

Don't worry about it, get the logging done, and graph it. Who knows it might be something really simple.