190e cosworth air flow sensor etc

hi
Can anyone tell me how to test the air flow sensor, voltage resistance etc?
What should the car do if the sensor is unplugged while running?
This al relates to idle problems. the car will start up and idle at 2000rpm and then settle back down when the exhaust temp light goes out. Is this just coinciding with start up enrichment finishing or does something else happen in the circuit when the exhaust temp light goes out?

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regards Dave

[Benzmac]

That high of an idle does not sound correct. I have seen where the air flow sensor will cause this. You should check between pins 1 and 2. There should be .9 dc volts when the engine is idling at 1,000 rpm.


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Benzmac:
Donnie Drummonds
1992 500E (very soon I hope
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

quote:

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Originally posted by Benzmac:
That high of an idle does not sound correct. I have seen where the air flow sensor will cause this. You should check between pins 1 and 2. There should be .9 dc volts when the engine is idling at 1,000 rpm.

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When idle is 2000 voltage is approx 0.6 and at 1000 only 0.1!
When ever idle is at 2000 if i disconect the air flow sensor idle returns to normal. Is this just the car reverting to fixed op mode or indicative of a faulty sensor?

[stevebfl]

Are you guys talking about a 190e 2.3-16? If so what are you disconnecting, the airflow potentiometer or the elctro-hydraulic actuator?

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Yes, 2.3 16v cosworth. I am trying to sort out what is causing the high idle. Idle sw contacts ok as are the decel switch.

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regards Dave

[Benzmac]

These readings sound off. I would replace the air flow sensor and recheck. When any problem is seen by the control module, the engine goes into FOM. (fixed operational mode) When this happens, the idle can be high or low depending on the idle valve. Usually it is high that I have seen.

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Benzmac:
Donnie Drummonds
1992 500E (very soon I hope
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Yes it seems to point to the air flow sensor which i think i will replace. The idle always drops to normal when i disconect the air flow sensor hence the assumption of the car reverting to FOM when i do this.
Do you also know where i might locate a lorinser alloy wheel, 16 inch, 205 tyre

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regards Dave