94 E420 high idle cold than - Mercedes-Benz Forum
 
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#1 Old 12-05-2012, 06:27 AM
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94 E420 high idle cold than

What is this problem, high idle,1300, than warms up it fluctuates 1300-800 every second

All I did is put good gas, than I noticed it. all vac lines look good, I have no check engine lite on.

Last edited by sthomen; 12-05-2012 at 12:44 PM. Reason: more info
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#2 Old 12-05-2012, 06:38 AM
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You do not give much information or history to this problem but the biggest cause of this is a vacuum leak.

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#3 Old 12-05-2012, 12:45 PM
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All vac is good
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#4 Old 12-05-2012, 09:09 PM
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Quote:
Originally Posted by sthomen View Post
All vac is good
How did you test for vacuum leaks?

ERIC
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#5 Old 12-06-2012, 03:15 AM
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Eyes, and ears. Is there a other way.
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#6 Old 12-06-2012, 03:21 AM
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Get a can of carb cleaner spray and start the engine from cold and spray small amounts over the vacuum area's such as manifold gaskets/vacuum pipes/fuel injectors etc and if there is a leak you will see and hear the difference straight away. Be careful not to spray this onto an hot exhaust as it is flamable.

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#7 Old 12-07-2012, 12:42 PM
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Quote:
Originally Posted by eric242340 View Post
Get a can of carb cleaner spray and start the engine from cold and spray small amounts over the vacuum area's such as manifold gaskets/vacuum pipes/fuel injectors etc and if there is a leak you will see and hear the difference straight away. Be careful not to spray this onto an hot exhaust as it is flamable.
OK did that nothing when it starts cold the rpm is 1000 - 1300ish than in about 4min the idle retards down to norm idle than up to 1000s. the change continues till you shut it off. the changes are intermitents in seconds. its a cycle the sounds like something it forcing idle down. This car has 145k, and has not been altered in any way. all factery.
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#8 Old 12-07-2012, 06:25 PM
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You will need to read the fault codes next, it may be the air mass meter but the codes will confirm or deny this.

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#9 Old 12-09-2012, 05:16 PM
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Ok, I will work on that next week. wont be driven. I did see a crack on the plactic frame that holds the wires in the mass air flow. the wires are still intact.
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