Having yet another problem with my 00 s4 project. Drove it for the frist time, and it felt real sluggish. Hooked up a boost gauge and noticed it was runing at 20 pounds vacuum at idle, and 0 psi under throttle. Did a leak check but found no leaks. What would cause total loss of booost. Are my turbos bad!!!! any ideas?

 

If your turbo's were bad you would hear them whining. Have you used vagcom on the car?
This is your first step. If your pulling codes for EGT sensors that could be your problem but typically you wont lose all your boost.
Your wastgates could be stuck open but thats unlikely for both.
Are you sure you dont have any boost leaks? i'd say VAG it then run another boost check.
could be in limp mode.

 

I thought about checking the wastegates. Just looked like a huge PITA to get my hand in there. Guess I will be doing this later, i'll also check the turbos for seizure and shaft play while i'm in there. I don't have VAG COM or have ever used it. Is the program expensive?

 

Not sure if there is a local seller. However, here is a website for them.

On another note, if you have a light coming on, then the local auto store can also check the code for you, for free.

Here comes a silly question I am sure you have already tried... Regarding the 0 psi, is the boost gauge hooked up properly?

 

Just a clarification, you are checking the boost in neutral? Turbo cars don't typically make positive boost pressure with no load on the engine (Although these turbos are teeny tiny and do spool up faster.) If you are indeed seeing 0 psig at part throttle, your turbos are ok (Maybe not great, but ok.) N/A cars will still show vacuum at part throttle. You need to check the boost while your driving. Sluggishness is usually attributed to excessively retarded timing or, in lesser cases, overly rich fuel.

 

Good point. I will try to read the boost level under power later today. As for the boost gauge, i hooked it up to the fuel pressure regulator. There was a post on how to do this somewhere on the forum. So my 0psi under throttle at neutral should be normal then. I just figured the turbos still have to make some boost wether in gear or not.

 

No, you need load on the car to make boost.

 

Just got my car back from the dealer on friday, and I now have boost!!!
Turns out whoever previously tinkered with the car, mounted the diverter valves
upsidedown!!! Regardless, I've only got boost up until 4k rpm. then it goes into some kind of limp or save mode (rpm won't go up and engine sputters). Took it to a local VW meet, and had someone scan the car with Vag Com. the computer threw codes for a MAF sensor. Just got a new one ordered. the guy also said the car was overboosting. can this be due to the MAF sensor? The exhaust smells strange as well? possibly o2 and MAF?