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  #1  
Old 08-31-2008, 07:42 PM
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Stumped in KS

Having high idle problems on my '83 380 SL. Hopefully someone can point me in the right direction.

Replaced the Idle Control Unit, the Overload Protection Relay, Idle Control Valve and vacuum hoses, along with the 42 degree C Engine Temperature sensor. Get 13.4 volts at ICU Connector pins 2 and 4.

Tested voltage at the Idle Control Valve connector and get about 11 volts.

Idle Control Valve clicks when tested.

Took the car out on an errand yesterday and when I started it up to go home high idle was gone.

Unfortunately whatever caused the idle to work was only temporary.

I'm stumped. From everything I've read it should work correctly.

Anyone have any suggestions on what to try next?

Thanks
Mark

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  #2  
Old 09-01-2008, 12:54 AM
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Forgot to mention that I replaced the Oil Temperature Sensor too.

This is driving me nuts. I've searched and read any previous posts I could could find concerning the high idle problem. Any help would be greatly appreciated.

Thanks,

Mark
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  #3  
Old 09-01-2008, 08:32 AM
83gray380
 
Join Date: Dec 2007
Location: chicago
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Go down several pages on this site and their is a long post on this exact subject. I believe the post is "380sl awakened with high idle". You will get lots of great information about the high idle issue. Good luck
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  #4  
Old 09-01-2008, 09:05 AM
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high idle

Where is your "economy" gauge reading at idle? If it is not pegged in the black (all the way to the left), you have a serious vacuum leak that could manifest itself as high idle.
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  #5  
Old 09-01-2008, 09:39 AM
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not sure , does yours have the air sensor on the air cleaner intake? If so disconnect and see what happens
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2015 Porsche Cayman - Elizabeth
2011 Porsche Cayman - Bond,James Bond
Sadly MERCEDESLESS - ALways LOOKING !
99 E320 THE Queen Mary - SOLD
62 220b - Dolly - Finally my Finny! Sadly SOLD
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
19 BMW X5 - Heaven on Wheels
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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  #6  
Old 09-01-2008, 01:44 PM
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Sorry, don't mean to sound abrupt, but post "380sl awakened with high idle" has never been posted a solution to the problem. I've eagerly watched that particular post for a possible solution. Maybe I missed something, is there a particular suggestion that you are referring to?

Economy gauge is all the way to the left at idle. No vacuum leaks that I can find and I've checked and replaced the Idle Control Valve hoses and several of the vacuum line connectors. To be sure there are no vacuum leaks I tested the lines and connectors with carborator cleaner.

Not sure what air sensor you are referring to but when I remove the air filter housing there is no difference in idle speed. Are you referring to the air intake breather hoses?

Please, keep posting possible solutions. I'm open to all suggestions.

Thank you very much,
Mark
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  #7  
Old 09-01-2008, 02:32 PM
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How are you measuring the voltage at the idle air valve?

You should be measuring it at hot idle with the connector slid back enough that you can touch your leads to the pins.

11 volts is a bizarre reading if you are measuring this way. The spec is 3-5 volts. I don't think the relay can put out 11 volts. But if it is, the valve would be closed almost all the time (it's a frequency valve) without slowing the idle down. So either the valve isn't working, or you have a large leak somewhere that's allowing "false air" into to the system.

Some other thoughts -

Is the throttle valve closing all the way - no interference from the linkage?

Have you tested the operation of the oil temp switch?
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'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #8  
Old 09-01-2008, 04:25 PM
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mine has a sensor on the air intake( air cleaner housing) ,it senses air temp and helps to adjust air flow, idle ect. Yours may not have it.
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Ron
2015 Porsche Cayman - Elizabeth
2011 Porsche Cayman - Bond,James Bond
Sadly MERCEDESLESS - ALways LOOKING !
99 E320 THE Queen Mary - SOLD
62 220b - Dolly - Finally my Finny! Sadly SOLD
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
19 BMW X5 - Heaven on Wheels
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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  #9  
Old 09-01-2008, 05:08 PM
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Quote:
Originally Posted by meltedpanda View Post
mine has a sensor on the air intake( air cleaner housing) ,it senses air temp and helps to adjust air flow, idle ect. Yours may not have it.
Your 72 has the D Jetronic fuel system. His has either the K Jetronic with lambda control or the KE Jetronic. Because it has an idle control unit, I'd guess it's the KE. Completely different animal, with different causes and effects.
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  #10  
Old 09-01-2008, 05:45 PM
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Correct. An 83 US 380 would be K-Jet with lambda.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #11  
Old 09-01-2008, 09:22 PM
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sorry I do have the D jet
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Ron
2015 Porsche Cayman - Elizabeth
2011 Porsche Cayman - Bond,James Bond
Sadly MERCEDESLESS - ALways LOOKING !
99 E320 THE Queen Mary - SOLD
62 220b - Dolly - Finally my Finny! Sadly SOLD
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
19 BMW X5 - Heaven on Wheels
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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  #12  
Old 09-14-2008, 01:54 AM
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Dumb rookie mistake...not all engine vacuum lines and rubber ends are obvious. I finally took the time to study the engine vacuum line routing diagram and follow each vacuum line end-to-end.

There where 2 vacuum lines connections hidden behind the air guide housing that were disconnected at the throttle valve housing.

To even see the connections you have to look to the right of the idle control valve, to the left of the thermal time switch, then down about 60 degrees with a flashlight.

Lower line is from a thermo-vacuum valve 50C and the upper line is from the charcoal cannister.

I replaced the two rubber vacuum line connectors that were oily, soft, and mushy then made sure there were no leaks in the lines themselves.

Putting the two vacuum lines back on was an exercise in patience and perseverance. Instead of pulling off the air intake I grabbed a pair of 10 inch hemostats and a flashlight and worked the lines into place.

I also replaced the two thermo-vacuum valves 50C and all of the other rubber vacuum line connectors that I could.

I've got to be getting closer to a possible solution because with a cold engine the idle is fine. Unfortunately, with a warm engine I've still got a high idle problem.

My next step will be to find the other well hidden vacuum line that runs from the switchover valve, mounted on the inside left fender, all the way across the front of the engine and disappears down to the smog pump area beneath the alternator. It should be connected to an air injector shutoff valve.

I'll keep posting as I progress to hopefully help someone else in the future.

Mark
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  #13  
Old 09-14-2008, 02:54 PM
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Nice wrench, getting those vacuum lines done with the air guide in place!
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Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #14  
Old 09-18-2008, 12:30 AM
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Thanks for the compliment. It was very frustrating task!

Finally got time to pull the alternator and smog pump so I could get a look at the air injector shutoff valve, check valve, hoses, and vacuum line.

What a suprise, nothing but rust. The smog pump hoses and the shut off valve had chunks of rust sitting in them. The vacuum line connector on the shut off valve was stopped up with bits of rust.

Ordered the parts to replace the air injector shutoff valve, the check valve, the smog pump and hoses so they should be here sometime next week.

Was hoping someone could tell me how to get the old check valve off the timing chain housing. The hex part of the valve is only about 1/4" wide and it looks like it'll take a 25 millimeter open end wrench to take it off. I've never seen a wrench that big that was so thin.

Does this take a special wrench or am I going to have to buy the correct size wrench and grind it down to fit?

Thanks,

Mark
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  #15  
Old 09-25-2008, 11:41 PM
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I messed up my parts order and didn't order the darn air injector shut off valve. Placed a new order so the part should be here sometime next week.

I did get the old check valve off the timing chain housing and the new one installed. It took a 27mm open end wrench that I ground thinner with a stationary belt sander. Worked perfect.

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