Sir Erl Seal et. al.

[quk@sievers.com (Phil Payne)]

In message <UPMAIL04.199611230507380607@msn.com> "Mike " writes:

> The 3B engine will run with the oil filler cap and dipstick removed.

Any engine can be set to do this.  The fact that an individual engine will is 
usually a symptom of vacuum leaks.  

> I don't see how a small leak from a seal will cause it to run as bad as 
> Lorens says his is.

You should have driven mine.

What happens is that progressively worsening seals admit ever more air into the 
engine and, via the breathers, into the turbo inlet.  This air is not seen by 
the air mass sensor.  Bear in mind that the mixture can only be adjusted at 
idle.  If there is a vast amount of air bypassing the air mass sensor, the fuel 
injection system won't see much air and won't provide much fuel - the mixture 
will be excessively lean.  Adjusting for a normal mixture under these 
circumstances biases the fuel injection system to be overly rich for the amount 
of air it sees.  When, subsquently, WOT cuts in further enrichment - the engine 
drowns in fuel.

> Lorens says he can hit WOT if he slowly applies the throttle, thereby
> keeping boost at a minimum. It would seem his problem is likely to be boost
> related and, as Peter pointed out, he may be hitting an inaccurate overboost. 

That's a new comment he made, and changes everything.  The 3B and the MB both 
have ECU boost control.  The frequency valve, manifold to frequency valve line, 
frequency valve to wastegate line, wastegate diaphragm, etc., all play 
significant roles here. 

But, given it's so simple to do, in his position I'd try just clamping that 
breather and see what happens to the mixture.  Only takes ten seconds.

 --
 Phil Payne 
 phil@sievers.com 
 Committee Member, UK Audi [ur-]quattro Owners Club