[W126 Coupe] HELP! Car Salling!!!!!

[Dick Spellman]

Hi David;

Glad to hear you found some improvement on the fuel filter change.  Any 
way you can test fuel pressures on the system to rule out the pump, 
regulator, etc?

As for the unstable idle...You may well have several gremlins occurring 
at once.  It should be relatively easy to test the throttle position 
sensor (TPS) using a VOHM meter.  If the idle position is not showing 
'closed' while the engine is at idle, then you could have a carbon 
build-up on the throttle body that needs to be cleaned or the TPS itself 
may have failed.

If the TPS shows open when it should show closed, just jumper the two 
pins on the harness to fake the 'at idle' position to see if this 
improves the stability of the rpms at idle.  The TPS is 3 pins total. A 
center pin which is 'common' and a pin to either side that reflect 'wide 
open throttle' (WOT) or At Idle.  Be sure you know which is which as you 
proceed with the test.  Then at least you will know what to repair 
before going further.  There are a number of other things that could 
cause that erratic idle as well but, this is one that's easy to check 
and rule in or out in making the repairs.

Dick

David Fatovic wrote:

>do you remember where you found the computer and
>wiring harness. I will want to check that out as well
>
>I changed the fuel filter tonight. it did make some
>difference. here is what I found while driving it
>tonight. it goes well while driving, but when you stop
>it doesnt hold idle very well or at all. that is when
>it will stall. it tries to idle around 480-500 rpm. I
>believe that is too low to keep vacuum pressure. what
>could cause this? I did replace the over voltage
>protection relay.
>
>any ideas now? what should I look at to adjust the
>idle?
>
>thanks,
>
>David
>--- mbcoupes-bounces at mbcoupes.com
><igatenby at optushome.com.au> wrote:
>  
>
>>-----Original Message-----
>>From: mbcoupes-bounces at mbcoupes.com
>>    
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>[mailto:mbcoupes-bounces at mbcoupes.com] I
>  
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>>had the same problem - swapped lots of parts between
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>my 500SEC (which had
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>>the problem) and my wife's 500SE.  In the end (after
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>months of chasing the
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>>problem) it turned out to be that small wiring
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>harness that attaches to the
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>>ignition computer - it had a wire that was broken
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>inside the insulation.  
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>>$15 at the wreckers' - problem solved.
>>
>>Ian
>>
>>The MB Coupes Website!
>>W126 SEC Mailing List
>>Postings remain property of MB Coupes, L.L.C.
>>    
>>
>
>The MB Coupes Website!
>W126 SEC Mailing List
>Postings remain property of MB Coupes, L.L.C.
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>  
>