Fuel & air mixture screw - Mercedes-Benz Forum
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#1 (permalink) Old 06-21-2012, 04:44 AM
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Fuel & air mixture screw

I had some work done at a shop and they said they played with the mixture screw on the throttle body. I can hardly sit at a light now without the car stalling. Where should the screw be so I can correct the problem instead of bringing it back to these idiots.
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#2 (permalink) Old 06-21-2012, 07:42 AM
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I had some work done at a shop and they said they played with the mixture screw on the throttle body. I can hardly sit at a light now without the car stalling. Where should the screw be so I can correct the problem instead of bringing it back to these idiots.
Take your air cleaner off, it's located here on the fuel distributor.


Provided your injection system is still functioning correctly, you should get a multi-meter with a duty cycle and then adjust according to this procedure: http://www.startekinfo.com/StarTek/o.../PDF/30006.pdf Job 7.3-105, subsection a. Browse the forums to find which pins on the diagnostic port you need to connect to.

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#3 (permalink) Old 06-21-2012, 11:21 AM
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Aww man...its a nightmare once they messed with the air fuel mixture. I have a factory sticker on my car that says it is preset at factory and do not adjust. You have to know what you are doing....and plug the volt meter set on duty cycle in that round circle with the cap by the ABS module. I would not go back to those guys anymore. Mechanics cheat by adjusting that screw instead of diagnosing and fixing the real problem. Make them pay for it....and take it to someone that knows 201s if you cannot do it.

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#4 (permalink) Old 06-23-2012, 09:43 AM
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yeah that mixture screw is always the fall guy when the mechanic can't find the real culprit
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#5 (permalink) Old 06-23-2012, 10:07 AM
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I had some work done at a shop and they said they played with the mixture screw on the throttle body. I can hardly sit at a light now without the car stalling. Where should the screw be so I can correct the problem instead of bringing it back to these idiots.
What work was done to your car? Yes, adjusting the mixture screw is just compensating for other issues, especially vacuum leaks. When the 2.3 is running right, you make them stall.
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#6 (permalink) Old 06-23-2012, 09:16 PM
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I had the oxygen sensor replaced because i couldnt seem to get the stupid thing out. I also asked for them to check for vacuum leaks cause I could tell the car was not running right. Well after saying that they couldnt find any leaks I got a call the next day saying oh we think we found one at the throttle body and we played with the mixture to try and get it running better. Well it hardly ran. After reading up on how to adjust it I think I have it back to normal and checking the duty cycle I have it back to 70% which seems to be the normal.
Still not running well enough to drive but I know I will never bring the car back there!
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#7 (permalink) Old 06-24-2012, 07:58 AM
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The first thing I would do is check the vacuum hoses going to and from the Idle Control Valve. You want good soft hoses with tight connections.
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#8 (permalink) Old 06-24-2012, 08:15 AM
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Quick thread jack... Where is the Idle control valve on the 2.6? ...thread jack over.
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#9 (permalink) Old 06-24-2012, 08:23 AM
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Quick thread jack... Where is the Idle control valve on the 2.6? ...thread jack over.
In front of the Fuel Distributor with a 2 wire connector plugged in to it.
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#10 (permalink) Old 06-24-2012, 08:50 PM
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In front of the Fuel Distributor with a 2 wire connector plugged in to it.
Thank you, sir!
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