2004 Audi A4 1.8T engine problems

[mannyo]

So my recently acquired 2004 A4 Cabriolet has a variant of the infamous 1.8T engine, with a number of problems.

 

I did a VCDS scan as the car is not running right, and cleared the codes. I've not rescanned it since but it has the following faults.

Stupid me forgot to make a note of the codes before clearing.

 

Random multiple misfires detected

Lean codes

Pressure drop between turbo and ????

Idle Speed higher than expected

 

Now the symptoms.

Start car and all is well when it is cold but it runs a little rough.

Once the car has warmed up it idles at between 1000 and 1200 RPM and refuses to drop to normal, also when revved up the revs drop really slowly.

 

I am guessing that unmetered air is entering the intake, and most likely causing all the faults, guessing this is a vacuum leak and the hoses are most likely 15 years old, but not sure where to start. 

 

I also have another two problems.

The Check engine light does not work, not even sure it has one. Guessing this may have been tampered with, but you cannot do an output test of the instruments in VCDS as it says unsupported when you click on output test.

 

The other is an oil leak, it's lost about 1 litre in 2K miles. It is leaking, from the exhaust manifold side of engine. Turbo is oil cooled, so maybe leaking from turbo area. Some pipework was changed at 88K miles by previous owner, I have the invoice which is to fix oil and coolant leak. Car no longer losing coolant, just oil.

 

Any thoughts as to diagnosis of faults, and where the common place for leaking oil maybe.

 

[TheClient]

Mmm. That could be quite a few things. Or what seems more possible is that there are a few problems.

 

It does sound like there is a vacuum leak. You could confirm with a gauge. Try to listen abound hose connections and problem items for sucking.

 

I don't know the pcv set up on the gen 1 ea888 but on other models it can lead to vacuum leaks and system lean.

 

When were plugs changed? Try moving coil packs to different location and see if misfire code follows suit. 

 

Also sounds like you may have a turbo to intercooler or intercooler to intake manifold leak. I'd be checking all joints. Can you hear hissing with Windows down and driving.

 

Also you could try making a post in mk2 forum with your engine code as a lot of the running gear will be shared with the mk2 of the same vintage and the main car forums get a lot more readership. .

 

 

[TheClient]

On the oil leaks:  you probably need to remove the engine undertray and the plastic intake tract in the engine bay at the back of the engine that leads to the turbo cold intake and an inspection mirror and see if you can pin point the source. There are feed and return oil lines that run to the turbo. Otherwise, if it is leaking from the intake air pipework that again points to a possible pcv problem. But I'd be surprised by the amount of usage from that if the PCV was the the only problem.

[SuperbTWM]

Regarding the air leaks. There are quite a few plastic items under the inlet manifold for the PCV system and are prone to leaking as well as pipes perishing, you either need to pressurise the system with air( you can make a home made rig and use an air compressor and go round with some leak detector spray or get a proper smoke test done.

 

 

 

Edited 9 November, 2019 by SuperbTWM

[mannyo]

Just to add, the engine code is BFB.

 

I did some checking at the weekend and cannot see anything obvious with the vacuum system, more investigation required.

[mannyo]

Some observations regarding the unmetered air intake.

 

I noticed the other day whilst driving with the window open that on WOT you can hear air from the front of the car.

 

So I think air is escaping after the turbo as the sound becomes more prominent as the turbo spools up.

 

I wonder if that could also be the cause of the running issue as I guess when running off turbo the intake could be drawing air in through the same leak.

[TheClient]

Either way a hissing sound from a boost leak needs to be fixed.  It could certainly cause the pressure drop code.  I would probably get the system smoke tested unless it is particulalry easy to inspect and make good every union in intake piping pre and post intercooler. 

[AlexBici]

Hello mannyo,

 

Did you was able to solve the problems with you Audi Cabrio 1.8t BFB?

I had exactly the same problem with my car. It was definitely an vacuum leak.

I solved this problem in my town at a local service.

To total costs was: 30 euros for the original vacuum lines and 150 euro for the manufacturing costs.

 

Moreover during the run test I have noticed that my car doesn't not run properly due to the bad unises valve that was install only on the BFB engines.