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Old 02-05-2002, 12:21 PM
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Join Date: Feb 2000
Location: Santa Clarita, CA, USA
Posts: 133
Thumbs up high idle speed fixed


I have a California 1991 420SEL with a check engine light. The X/92 diagnostic connector on the firewall close to the battery has an LED that displays 9 flashes when the button is pushed for 2-4 seconds. I would appreciate a table for the trouble codes on this car.

Your help is appreciated...thanks.


Last edited by DieselGuy; 08-25-2002 at 01:08 PM.
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Old 02-05-2002, 01:16 PM
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Join Date: Feb 2000
Location: Santa Clarita, CA, USA
Posts: 133
Ok I was able to clear the code by holding down the button on the X/92 connector for approx. 10 sec.

I attempted to diagnose the engine electronics. Here's what I gathered:

With ignition ON, engine not running:
EHA: 60mA
Duty Cycle on pin#3 of X/11: 85% (correct for Calif. car)

On Cold Startup:
EHA (while cranking): 70mA

Warm up:
EHA: mA gradually decrease over a period of a min., min. and a half
Duty Cycle on pin#3 of X/11: steady at 54%
Idle Control Valve: 990-1000mA
RPM at pin#1 of X/11: 980

Operating Temp:
EHA: hovering back and forth around 2-3mA
Duty Cycle: hovering back and forth around 54%-62%
Idle Control Valve: 990-1000mA, with A/C on 920 mA
RPM at pin#1: gradually increasing to 1130

The car suffers from a high idle speed and hard cold starts. Cold crank times around 5-7sec.

I'm trying "real" diagnostics... what's the probable cause for the high idle? I examined the Idle control Unit under the front passenger foot rest. Pulled it out and cleaned it and resoldered the joints. No change in idle performance. Also cleaned the idle control valve and put new hoses on it. Still no change.

Any help is appreciated as always...thanks

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Old 08-25-2002, 01:19 PM
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Join Date: Feb 2000
Location: Santa Clarita, CA, USA
Posts: 133
high idle speed fixed

Update: The car was taken to an independent shop to confirm my speculation about a faulty idle control valve. $500 later ($400 for the idle control valve), idle is back at 600-650. Pretty expensive confirmation of all my "diagnosis." I didn't want to shotgun parts though. My friend is happy even though he felt a little ripped on the price of the valve.

Here's a related problem that was also fixed by the idle control valve. -->

1991 420SEL Fails CA emission due to advanced timing

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Old 08-25-2002, 06:14 PM
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,768
For future reference, I believe code 9 is shorted/open air intake temp sensor...
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