[T3] On my 73 square

[Jim Adney]

On 13 Sep 2019 at 16:11, William Jahn wrote:

> I will check the voltage at the ECU from the power relay , to be
> honest after I fixed the relay plugging in the air temp it seems to run
> even worse and the same with it unplugged.

Fixing the supply voltage should have made it run leaner, which normally 
would have made things better. Your observation that it's worse now, makes 
it seem even more likely that it's running excessively lean, which is 
consistent with removing the air temp sensor, which richens it up a bit.

This is also consistent with the problem starting as the engine and head 
sensor warm up and lean out the mixture.

Things that will make it run lean:

Vacuum leaks at the air runner to head connections. (I'm pretty sure you 
have fixed those, but did you get both surfaces nice and clean and flat 
before you installed the new gaskets? You could also check with some 
propane there.)

Low fuel pressure (measure while driving)

Bad connections in the injector circuits (Measure the resistance from the 
ECU injector pin to the separate ground pin on the same connector, should 
be ~2.5 Ohms. Also make sure the brain connector fingers are close enough 
that they will make good contact with the brain circuit board. I have some 
little bits of brain edge connector that you could use to test the tightness of 
each conector pin.)

Leaky aneroid in the pressure sensor (try a different, late (116) E pressure 
sensor) This is rare, but it happens.

That's all I can think of at the moment, but there may be more.

> I don't have a problem spending the extra time checking wires with a
> DVOM. 

The Bosch tester essentially gives you 1 or 2 extra hands. You can set the 
tester to look at a particular resistance path, while you watch the needle as 
you wiggle wires to look for intermittent/weak connections. It takes 2 people 
to do this with a DVM.

If you don't have the Bosch tester, get a friend to help.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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