Parts fiche error (and other things)

[quk@isham-research.demon.co.uk (Phil Payne)]

I had a visit yesterday from a UK ur-quattro MB owner, anxious to try and 
discover why his car occasionally cuts out.  think We found the problem (see 
later) but he had also found an important error in the spares microfiche.
 
According to the microfiche the part numbers for timing belt, cam pulley, water 
pump and harmonic balancer changed at chassis 85-JA900644 onwards.  The later 
design has a different tooth profile and is somewhat wider - it's supposed to 
last longer. However, as those of us who have been paying attention here know, 
there was a special series of late MB ur-quattros fitted with quite early 
engines, just before the series that seems to have a 20V chassis but an MB 
engine.

The rule in the microfiche should properly be "if VIN is 85-JA900643 or below, 
OR engine number starts with MB0013xx - use the older part numbers".  I'll be 
writing to Audi AG about this error.  

I had a good chance to look over this engine - it's the first MB0013xx I've 
seen in a late car.  It really _IS_ an old engine and not just an old block, so 
the jokes about "Herr Direktor .." take on new meaning.  The plumbing (e.g., 
WGFV boost tap) is 'old' style rather than 'new'.  I thought at first that the 
problems the owner reported might be down to an old engine and new ECU 
combination, but a few test runs with Scott's gizmo's and my spare ECU attached 
dissuaded me.  The car's ECU had been opened and some of the tracks scratched, 
but the chip was original.  I didn't realise before that the MAC12D even uses 
the same circuit board as the MAC11.
 
The symptoms are that WGFV operation starts normally at WOT, but as revs and 
speed build it suddenly stops.  Boost continues, and then the fuel pump starts 
intermittent cutouts.  I've never seen an ECU _stop_ WGFV operations with WOT 
engaged before, and I started to suspect a mis-reading inlet air temperature 
sensor or intermittent WOT switch.  Wrong - it's 492 ohms at the sensor and at 
the ECU connector. The only code stored is 2224.

The car has passed every electrical test from the ECU plug and ISV controller 
socket inwards.  The on-board diagnostics run clean.  WGFV is air-tight in both 
directions.  All vacuum lines and the ECU diaphragm are also air-tight 
(MityVac).

The only area of suspicion I have is the wastegate spring.  It seems _far_ too 
strong for an MB wastegate - I estimate it took me 40 to 50lbs of pressure to 
get it closed enough to take a couple of the securing nuts, plus there was a 
nut missing when I stripped it.  Anyone care to comment on MC/MB/MC-2 spring 
pressure?  How much does it take to get the wastegate cap back on?  Has anyone 
seen a spring with a blue colour code?

I posted the basic dimensions of the spring last night.

BTW - this is a _nice_ car.  It's Pearlescent White, and has done just over 45k 
miles.  The paint is immaculate (serious but well-repaired front end accident 
damage) but it desperately needs decent tyres and a four-wheel alignment.  The 
interior is _genuinely_ in showroom condition.

-- 
 Phil Payne
 UK Audi [ur-]quattro Owners Club