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Discussion Starter · #1 ·
Having problems with my 300E 4matic 1990. When cold it starts pretty easy , runs at 1000-1200 rpm and all is good . After some time , when warm it loses idle speed , drops to 500 rpm and stalls. Happens if i stop in gear or i leave it running (but it takes longer then) .Easy start after stalling no problem . If i stop it from stalling by giving it fuel it hesitates for a moment and then all is good . This is only a problem while idling, it has not stalled when driving yet ..
Also there seems to be some kind of strange surge in the electrical system when started . Maybe 1-3 seconds after car starts and radio is on , radio dies and lights for a moment .. ??
Changed opv and fixed cold start problem(blown fuse) and got hot idle problem instead ..
Checked icv valve and it moved freely but did not close fully . Should it ?
Switch on throttle linkage works fine .
Have been looking over vacum lines and have not found a culprit yet , exept maybe the two wich come out of the cylinder head and connect to the top air filter box and an L shaped one wich connects to the head itself.. They were pretty hard ant had cracked ends ..
New plugs ( the correct ones) , Cleaned distributor cap and hammer..

Have looked repeadly and not found solutions fore these problems..
 

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2013 E350 sedan, 2013 E350 cab, 1993 400E sold,1999 ML320
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2,454 Posts
1000 rpms is too high for idle. Suggest changing coil and wires as a tune up is normally the biggest culprit.
 

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Discussion Starter · #3 ·
Nope , 1000-1200 is fine when cold . Read all the post. I don´t belive ignition has anything to do with it .
 

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2013 E350 sedan, 2013 E350 cab, 1993 400E sold,1999 ML320
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OVP, Coil and duty cycle do a search biggest issues for poor running. Vacuum leaks also. My dad always had me use a hose and water to spray around them with car running slightly if idle changes then you know. I have heard there was a way with brake cleaner doing the same thing. I went the non flamable way.
 

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Discussion Starter · #5 ·
I did a vacum leak serch today . used low pressure air to test some lines and all i culd see with brake cleaner with the car running .. Found nothing.. Have not measured duty cycle with the car running and ajusted idel . Didin´t want to mess with it if i was missing something.. ..
Anyone know if icv should close fully ?

Unplugged icv while running ...ran worse..
Unplugged 4 pin temp at back of engine.. ran worse

Wich plug should i use for measuring duty cycle , the one by the battery or the round one on the other side of the engin bay ?
 

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1988 300TE 280,000 Miles
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198 Posts
Vacuum leak will cause Idle to go high.

Your IAC valve not closing all the way is not a problem either. If it closed any further, Idle would drop more.

I found this thread because my idle is high "sometimes".
 

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86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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Plank,

Use the search function of this forum for "air/fuel ratio adjustment". You will have plenty to read. Also, I might suggest you put a volt meter on your battery with the car running. If you get a reading of less than 13.4V, you have a dying voltage regulator. These cars are very sensitive to correct voltage. The regulator is dead simple to change in all of about 10 min. with a phillips screw driver.

Anything else you can share about the maint. history of the car will be very helpful. Last tune up, what was done, type of plugs you are running and so on. The last thing anyone wants, especially you, is to throw money at problems. More information = less guessing.

Good Luck,

Jayare
 

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Discussion Starter · #8 ·
Mmmm .. Would a bad battery affect how the var runs ? I measured the current while running and it was close to 14v . . . can´t say about tuneups or what previus owners did ..
Only had it for 4 months ..
 
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