Idle control unit - Mercedes-Benz Forum

 
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post #1 of 8 (permalink) Old 06-10-2010, 12:04 AM Thread Starter
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Idle control unit

hey, my 300se has a bit of a unstable idle so im assuming its the idle control unit. does anyone know where it is located in the car?

cheers for any help.
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post #2 of 8 (permalink) Old 06-10-2010, 06:06 AM
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unstable idle

Bad assumption. Look for a vacuum leak first. Most common and easiest/cheapest to fix.
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post #3 of 8 (permalink) Old 06-10-2010, 07:00 AM
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Originally Posted by rocky raccoon View Post
Bad assumption. Look for a vacuum leak first. Most common and easiest/cheapest to fix.
I totally agree. Mine was doing the same thing and we cleaned the ICU and fixed a few vacuum leak's. It idles much smoother now.

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post #4 of 8 (permalink) Old 06-10-2010, 07:05 AM
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Purpose of idle control unit is to provide extra air when engine is running "on choke," i.e. after a cold start when idle mixture is richer than normal.

Kent Christensen
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post #5 of 8 (permalink) Old 06-10-2010, 08:11 AM
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Which 300SE? A 300SE can be from the 60s (112), 80s/to 91 (126) or early 90s (140). Depending on which model it is it may not even have an idle control valve.

Last edited by deanyel; 06-10-2010 at 08:13 AM.
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post #6 of 8 (permalink) Old 06-14-2010, 04:10 PM Thread Starter
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Which 300SE? A 300SE can be from the 60s (112), 80s/to 91 (126) or early 90s (140). Depending on which model it is it may not even have an idle control valve.
it is the w126 1987 300se. i will have a look at the vacuum hoses tonight. it there a easy way to check the hoses?
cheers
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post #7 of 8 (permalink) Old 06-14-2010, 09:25 PM
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How to check for vacuum leak's.

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Originally Posted by patrickgledhill View Post
it is the w126 1987 300se. i will have a look at the vacuum hoses tonight. it there a easy way to check the hoses?
cheers
Just look at each hose separate and make sure they don't have any cut's/hole's etc. Look for hose's that have come off and are no longer connected and then.. reconnect them.
You can always use the starter fluid trick by spraying around hose area's and if the idle raises, then it's sucking the fluid in somewhere and burning it. That would be a leak. That's also a good way to check if an intake manifold gasket is leaking.

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post #8 of 8 (permalink) Old 06-14-2010, 10:28 PM Thread Starter
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checked all hoses ect. but it is still very unstable. the most it will raise to is 1500 and the least is 500. also when you accelerate hard in park or neutral it will rev up have a slight pause and rev all the way. could it be a fuel filter or pump? sometimes it takes ages to start as if no fuel is reaching the injectors.
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