We just pulled the passenger seat out of the Yellow Peril so we can get to the
'puter. We're currently down with a bad master cylinder drooling into the booster.

No matter what we do the mixture is VERY rich, stinky exhaust, black smoke, etc.

I have screwed the center screw of the Manifold Air Pressure Sensor all the way
in, which should in theory make the normal running very lean. I have turned
the control on the ECU all the way counterclockwise which should make the idle
lean. I have shorted the leads of the coolant temp sensor together, which
corresponds to a temp of well over 120°F, so everything SHOULD be so lean it
would not even approximate running normally. But it not only runs but it still
has the stinky exhaust and black smoke, black spark plugs,etc.

Next plan is to start checking leads on the 'puter to see if maybe something
is not getting through, especially the coolant temp sensor. Any other
recommendations would be GREATLY appreciated.

BTW our local Bumper-to-Bumper store claims they will have our new/rebuilt
master cylinder tomorrow afternoon and the price is around $35. I was shocked!
We'll see what it turns out to be!
--
George Downs, Bartlesville, Oklahoma, Central US

What about the cold start valve, Checked the thermal timer?

Make sure the fuel pressure is within spec.

Regards


Pete

Fuel pressure is good, cold start injector not getting a signal
and thus nonfunctional. Therefore the thermal timer's not doing
anything either.

I changed the 'puter and the MAPsensor and it is now responding to
adjustment but still some problems - see later post
--
George Downs, Bartlesville, Oklahoma, Central US

Also check that the return line from the fuel pressure regulator to the tank is clear.
Wiring and resistance for the air temp sensor ok? It only has a minmal effect on mixture so probably has nothing to do with your problem, but might be worth a look anyway.
I reckon you've already checked this, but it might be that one or more of the injectors are stuck open.

Fuel pressure is rock steady. Air temp sensor OK.
Changed 'puter and MAPsensor and it is now responding to adjustment.
More in later post.
--
George Downs, Bartlesville, Oklahoma, Central US

George,

I know you're probably tired of hearing this, but you need to try swapping in a "known good" MAP sensor. Just because it doesn't leak when you suck on it doesn't mean it isn't shot.

Here's a scanned manual someone put on the internet. I think it covers both D AND L-jet. Hit the link for images number 12 & 13 for MAP info.

http://www.conservatory.com/vw/manuals_nyx/EFI-DL.html

Here's another document that talks stricktly about the MAP sensor. This is probably the best info I have ever seen on that part of the system:

http://members.rennlist.com/pbanders/manifold_pressure_sensor.htm

It seems as though all sources seem to say the same thing about testing the resistance:

"The coils can be tested by measuring the resistance between terminals #7 & # 15 (should be about 90 ohms)and between #8 & #10 (should be about 350 ohms)"

Sucking on the hose connection should result in some sort of change in resistance, but I don't know what. I believe the second link I gave you above has some sort of graph that relates vacuum change to resistance change.

I have one or two spare MAP sensors at home. I'll give them the "suck vs resistance" test in the next couple days and let you know what I observe.

I ended up changing both the 'puter and the MAPsensor and finally got it
to respond to adjustment. The resistance shown by the manual is about what
all mine show but resistance measurements of coils are pretty minimal in
value - show open or shorted and that is about all.
I'm putting up another post.
--
George Downs, Bartlesville, Oklahoma, Central US