kb03gt

A few days ago I purchased my first Audi. I have always been a fan and found a very nice looking 2004 A4 1,8t 6 speed quattro. I drive 162 miles daily for work and yes it is worth it lol. The guy I purchased this audi from was building it for his son, but the kid went and leased a car getting impatient awaiting the engine swap to be done on this one (broken timing belt). He put a solid 3k or more making this thing back to being road worthy. The new engine has only 77k on it. Well on my test drive I noticed that it would start to boost then instantly hit limp mode and cut the turbo back. I talked him down even more and now I am fighting this.

- Took it to a reputable German shop a few towns over. They said it was throwing a maf and a 02 bank one lean code. They did a throttle body adjustment and said it felt good. On the way home it never once felt "good". They also claimed it held vac.

- Yesterday I replaced the MAF, and obviously there was no change. I cleared the codes and crossed all my fingers. Pulled out of the parking lot n gave it hell. Spooled up nice through first gear. Woohoo it's fixed right? Nope. Second gear it cut out again with the sound of detonation (pinging) from the engine.

Here are the things I noticed:

- Brakes feel hard when push harder than a regular stop.
- There's a hose on the drivers side of the engine thats cut and going nowhere. Much larger than a reg vac hose.
- There is a small exhaust leak that's barely noticeable towards the front of the car.
- The turbo cuts in and out almost continuously through acceleration 1/2 pedal or higher.
- I've owned many turbo cars in my life but this one sounds a bit different. It is my belief that in order to hit limp mode the turbo actuator controls the limited boost and not the diverter valve?

I think this engine job was one that would be considered a "hack". It was done at a Audi dealership and I would expect much higher quality (looks like someone just didnt give a eff).

Any insight on where to start (I am assuming that missing hose). Thanks for any insight I am so happy to have this audi!

old guy2

You have a boost leak. Here's a DIY that can help you find it. Clicky click®

kb03gt

This hose has seen better days. Cause possibly?

old guy2

That would definitely cause your lean code but it would not be a boost leak. That hose is part of the block breathers and being split would allow un-metered air to enter into the intake system. It isn't a pressurized hose. You should still perform a boost pressure test.

kb03gt

I replaced the bad hose shown above with a generic but sealed well. Well, I did the boost leak test. I couldn't hear anything minus a bubbling sound. So I started to move hoses around and I could hear hissing from the top one by the intake manifold. But I physically had to move it. I suppose it's possible that under load there is enough vibration there to disrupt the seal. I've owed a few tdi Jettas before so I am semi familiar with the systems function of attaining boost. I'm just at a loss.

old guy2

I suspect the issue isn't with the hose but with what connects to the right side of the hose. That would be your SJP (Suction Jet Pump). It's a vacuum amplifier that helps with providing adequate vacuum for your brake booster. It's also a known problem component. I see that yours has already been replaced once already. If it leaks it will cause a loss of brake boost pressure thus causing a stiff brake pedal.