Comsa

I own a 2000 Audi S4 that's got everything you can think of in it. Lately the car seemed like it lost a little bit of boost with the turbo, and made an insanely loud whistling noise while accelerating. I called around and most places said it's most likely a boost leak, and there could be a problem with hoses, pipes, etc. And that the turbo is most likely not going out. But later that night my buddy took it for a spin with 5 people in the car, so it was pretty heavy. He gunned it, the check engine light came on, and the boost was poor. When we parked there was a VERY odd smell coming from the car, and the engine idle noise was more of a thumping than a clean smooth idle.. The exhaust pipes were shaking, and the engine was also shaking a tiny bit. When you sat in the car it would shake also. As we pulled out to head home, we put the pedal down and the car would go slower than a tank, the boost was not coming in at all, and the car would shake violently. The whistle noise also has stopped. It's for sure not a random misfire, but i'm wondering if a turbo has blown? But then why would the car shake, and why is the exhaust idle thumping? Somebody please Help me! Thanks.

S4andTLS

Well you really should eyeball/yank on/inspect all hoses and clamps and vaccuum lines

shawnoc2003

Could be a simple as fouled plugs if the ECU was adding the fuel needed to mix with the air that never made it into the cylinders.

Disconnect the MAF and pressurize the system with 10psi. If its a boost leak you'll find it right away.

If you have stock intercoolers, check the end caps - I had one leaking at the flange due to the flange crimp opening up.

For 2000, also check the TBB.

By the way, if you hear a leak - its best not to put it to the floor.

Python021

that doesnt sound like just a boost leak, it may have been leaking around a over tightened clamp on one of the bigger hoses, and then wen it drove like a tank thats most probably because the hose ripped(big tear)or popped off. there fore not delivering any boost. could very well be the intercooler as mention, but check turbo hoses from exhaust, charge hoses after turbo. should be one of them.

donromani

My first thought is a torn TBB but the "slower than a tank" symptom could also be the MAF. The MAF does not explain the loud whistling though, but the MAF failure could be a coincidence.

If the MAF is toast then the car won't make much boost which would explain why the whistling sound suddenly went away.

thejulex

Check of for massive boost leak/completely torn hose. Sounds like massive amount of unmetered air is getting into the intake causing the Air/Fuel mixture to be completely off . Since the engine can't really rev up on that there is also no boost.

On a healthy car the boost comes at 2500+ rpms, but yours is misfiring badly so you would probably be well north of that to have any boost on... ofc since your piping is leaky you will see no boost at all anyway.

Thanks!

Indyxtype

I had similar symptoms when my lower intercooler hose came off. I agree with the above that it is most likely a massive boost leak. Try unplugging the MAF. If it runs smoother (but still weak) that will help to confirm the diagnosis of a massive boost leak.