[Diy_efi] Bosch DME trouble...

[Mike Sharp]

Hi,

In case you missed my last email...

Porsche 924S, Bosch L-Jetronic w/Lamba control, Motronic
The car starts and runs reliably (its drivable) for the 15-20 seconds it 
takes to switch from
cold-start to warm-up mode.

Per the Porsche shop manual:
  . grounding all around the system has been verified
  . Power to the DME control unit is correct
  . Fuel pump runs
  . The speed and reference mark transmitters have been verified via 
'scope and have sufficient signal strength
  . Temperature sensors I & II have been verified via resistance checks
  . The throttle switches (both throttle closed & wide open switches) are OK

What does look out of spec are the voltage readings on the air flow 
sensor.  The shop manual says >8V across pins 9 & 6 (with the flow 
sensor & motronic connected) on the Motronic.  I've got 5.5V.  I swapped 
out both the flow sensor and the computer for other good units and the 
resutls are the same.  I verified that the harness between the Motronic 
and the air flow sensor aren't shorted or corroded.  With the hardness 
disconnected at both the airflow sensor and the Motronic the resistance 
plug-to-plug is minimal (a couple of ohms) and resistance between pins 
is infinite so I can't account for the voltage difference relative to 
what the shop manual says.

So what am I missing?  

    --Mike



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