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

[Dick Spellman]

Hi David:

Yes there is a vacuum hose on the intake manifold that runs down to the 
transmission vacuum modulator.  If it's loose or disconnected you will 
get a hard (almost like a bang) shift between gears.  If you say that 
the car is hanging in lower gears too long then I'd start by adjusting 
the Bowden cable and check all of your engine regulating linkages for 
proper adjustment at the same time.  If you then notice a lag between 
shifts I'd work the vacuum modulator (T) adjustment to get the correct 
shift firmness.

Was this car doing this before as well???  Have you checked the trans 
fluid level?  When was the last time the tranny and torque converter 
fluids were replaced?

Dick

David Fatovic wrote:

>Are there any vacuum hoses that connect the vacuum
>system to the transmission?  I got it to the point
>where it wont stall anymore, but it has some bit of a
>hard time shifting up.  It will sit in the lower gear
>at 3K RPM.  When I lift my foot off the gas it just
>keeps gear and slows the car down.
>
>
>Thanks,
>
>David
>
>--- Dick Spellman <spell.yy at verizon.net> wrote:
>
>  
>
>>David:
>>
>>When you say you cleaned under the throttle plate,
>>you were referring to 
>>the air volume meter???The plate just under the air
>>cleaner?  The 
>>throttle body is at the very bottom of that entire
>>assembly.  It's the 
>>first item bolted to the intake manifold.  If that
>>throttle plate does 
>>not fully close the TPS will see an 'open' which
>>will mean that the idle 
>>will sit lower than normal.  The idle may stumble a
>>bit where it's lower 
>>than prescribed.  If you put your foot on the
>>accelerator while in park 
>>and bring the rpms to say 650 (normal idle) is the
>>engine nice and 
>>steady?  If it is, you need to test the TPS and I
>>think you'll find it's 
>>simply a carbon build-up on the throttle body
>>preventing the plate from 
>>closing fully and the TPS from reading 'closed'.
>>
>>To test for a vacuum leak, remove the air cleaner
>>assembly, take a spray 
>>bottle filled with water and work the spray a bit at
>>a time all around 
>>the intake manifold and vacuum lines/valves along
>>the driver's fender.  
>>If you hear/feel the stumble worsen or get better
>>concentrate on that 
>>one area to route out the leak.  I do not recommend
>>spraying carb 
>>cleaner or solvent because it eats at the rubber
>>fitments over time.  
>>Another way is to take a propane torch (not lit) and
>>open the valve and 
>>work around the intake to see if the idle smooths
>>out at any point.  
>>Test each of the injector seals or fuel rails in
>>this manner as well.  
>>Stay away from the hot exhaust and spark plug wires
>>where you can.   
>>Jonathan pointed out to me some time back the
>>frequent failure of the 
>>purge hose that goes into the driver's fender.  
>>That's an easy check, 
>>just pull the fat short rubber hose and see to see
>>if it has a dry loose 
>>fit.  Another vacuum leak I found was the headlamp
>>elevation vacuum 
>>circuit.  On one MB it was the dash dial and on
>>another the vac line to 
>>the passenger headlamp.  Easy enough to pull the
>>lines at the dash just 
>>behind the elevation dial and close them off to see
>>if that makes a 
>>difference.  A Mighty Vac does help if you can get
>>your hands on one for 
>>some of the line tests like the headlamp vac
>>circuit.
>>
>>The air slider hoses can dry out and leak.  Keep at
>>it and you'll find 
>>the problem(s).
>>
>> David Fatovic wrote:
>>
>>    
>>
>>>It sits towards the middle, closer to the left as
>>>looking at it.  
>>>
>>>I took my lunch break today and pulled the Idle
>>>Control Valve and cleaned the shit out of it. 
>>>      
>>>
>>Almost
>>    
>>
>>>litteraly.  I also cleaned under the throttle
>>>      
>>>
>>plate. 
>>    
>>
>>>Now on my way back to the office the car did not
>>>      
>>>
>>stall
>>    
>>
>>>on me once, even when warm.  However, idle did get
>>>close to it.  The idle did drop below 500rpm a
>>>      
>>>
>>couple
>>    
>>
>>>times at a light.  It was also rough.
>>>
>>>So now the question is.  I assume I have a vacuum
>>>      
>>>
>>leak
>>    
>>
>>>somewhere that is messing with the idle a bit.  It
>>>      
>>>
>>is
>>    
>>
>>>also making it rough.  What is the easiest way to
>>>      
>>>
>>find
>>    
>>
>>>a vacuum leak?  I don't have any vacuum test tools.
>>>      
>>>
>>>Where are the usual leaks found?  
>>>
>>>David
>>>
>>>
>>>--- "Shayegan, Richard" <rishayegan at davidson.edu>
>>>wrote:
>>>
>>> 
>>>
>>>      
>>>
>>>>With the car stopped, engine running, in D, where
>>>>        
>>>>
>>is
>>    
>>
>>>>your economy gauge? Anything other than pegged at
>>>>the best fuel mileage side (i.e. the non-red side,
>>>>IIRC the left side) means a vacuum leak.
>>>>Richard
>>>>
>>>>________________________________
>>>>
>>>>From: mbcoupes-bounces at mbcoupes.com on behalf of
>>>>David Fatovic
>>>>Sent: Tue 6/6/2006 1:36 PM
>>>>To: Mercedes Coupes Mailing Lists
>>>>Subject: Re: [W126 Coupe] HELP! Car Salling!!!!!
>>>>
>>>>
>>>>
>>>>Would a vacuum issue also cause some sluggishness
>>>>going from a standstill to the first part of
>>>>accelleration?
>>>>
>>>>David
>>>>
>>>>--- Dick Spellman <spell.yy at verizon.net> wrote:
>>>>
>>>>   
>>>>
>>>>        
>>>>
>>>>>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:
>>>>>
>>>>>     
>>>>>          
>>>>>
>=== message truncated ===
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