Hesitation in hot outside air temperatures - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 11-09-2010, 12:45 PM Thread Starter
BenzWorld Junior Member
Date registered: May 2008
Vehicle: 1991 Mercedes Benz 300SL
Location: Hartwell, GA
Posts: 7
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(Thread Starter)
Hesitation in hot outside air temperatures

Hello All,

I am a new forum participant so I hope I am doing this correctly...

I own a 1991 Mercedes Benz 300SL. When outside air temperature reaches approximately 95 degrees Fahrenheit, at a stop, my RPM's drop to a little over 500 and the engine falters {RPM's vacillate slightly}...when I start from a stop, the engine "sputters", then "catches" and all is well...but it nearly stalls which is very dangerous at a busy intersection...I have to flutter the gas pedal to encourage it to go!

This does not happen in cooler weather.

WIS says, under "Poor throttle response at high outside temperatures", which seems to fit the situation, that the "Cause" is "excessive formation of fuel vapors" with the "Remedy" stated as "Install vent valve in regeneration lines between regeneration valve and engine" with a "Note" that says "Install vent valve with flow direction from tank to engine".

First, has anyone had the same problem and , if so, what did you do to cure it?

Second, if you installed a "vent valve" as suggested by WIS, exactly where did you install it; did your car already have a vent valve just after the gas tank, and, if so, did you install another vent valve? WIS call for part number "124 476 04 32", a replacement for "201 476 01 32".

Also, there seems to be a semantics problem that I encountered in my search for a "vent valve" in that some sites suggest that the regeneration valve and vent valve are "one and the same" which is not true.

Thanks for any and all input!

cbj625 is offline  
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post #2 of 2 (permalink) Old 07-20-2013, 07:11 PM
BenzWorld Junior Member
Date registered: Jul 2013
Vehicle: 2002 mb c240
Location: las vegas,nevada
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poor throttle

Hi Guys, I am new to this forum, and I am having the same problem. I have a 2002 C240 that has a poor throttle response only when its hot in summer, I live in las vegas and it gets hot here. I hope some of you guys will response and help. thanks in advance. Ed.
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