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  #1  
Old 08-31-2018, 12:52 PM
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om602 idle too low

Hi all,

seeking your thoughts on my latest issue.
1992 300D 2.5 turbo om602 361,xxx miles. egr delete and pressure wastegate.

headed home from work the other day everything is fine. Rolling on the highway 85mph, AC Blasting. Chillin'

pull off the exit to go up the hill to my house and there's a problem.
sitting in traffic waiting to get through a light and engine RPM are down at idle.
right about 450rpms.

I was immediately concerned so i pulled over real quick and just did a quick visual check under the hood. nothing obviously amiss. no smoke, fumes, leaks, sounds, smells out of the ordinary.

continued on to the house and shut down. Came out later and checked some more. oil looks fine, coolant looks fine, fuel looks fine. fuel and air filters are recently changed.

Apparently nothing wrong mechanically. I've looks all over the linkages and everywhere under the hood and have not found anything the looks out of the ordinary. just the low idle. each time i've started since then same thing with the low idle. Drove to work this morning no problems at all out on the road as long as i just kept my foot on the pedal to keep the idle up a little bit when i was stopped.

any ideas?
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1992 300D "IceBerg"
1984 300D "Blues Mobile"

1978 300CD "El Toro" Gone on to be born again
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  #2  
Old 08-31-2018, 01:17 PM
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Location: Barrington, RI
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My understanding is that the idle on your car is controlled by the computer (in fact, that's all it does now that you've done the wastegate conversion). So that would be a possibility.

Here is the procedure for testing the computer (the EDS):

http://www.w124performance.com/service/w124CD1/Program/Engine/602_603/07.1-1120.pdf
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06 E320 CDI "Benson", Platinum Blue, 173k mi
06 E320 CDI "Rutherford", Black, 143k mi
91 300D "Otis", Smoke Silver, 128k mi
98 E300 "Murray", Silver, 128k mi, Stage 2 Rocketchip chip tuned, under son's care

Twelve other MB's owned and sold
2002 Honda Odyssey 241k mi (want to name it "Homer," wife won't let me)
1961 Very Tolerant Wife

Last edited by shertex; 08-31-2018 at 02:14 PM.
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  #3  
Old 08-31-2018, 01:40 PM
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Location: Carolina
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That is my understanding as well. I don’t know much about it. I’ve read a few threads on idle problems. “Hunting” idle seems to be a common failure mode
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Current fleet
1992 300D "IceBerg"
1984 300D "Blues Mobile"

1978 300CD "El Toro" Gone on to be born again
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  #4  
Old 08-31-2018, 02:14 PM
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Quote:
Originally Posted by Phillytwotank View Post
That is my understanding as well. I don’t know much about it. I’ve read a few threads on idle problems. “Hunting” idle seems to be a common failure mode
Just edited my post to include link to test procedure.
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06 E320 CDI "Benson", Platinum Blue, 173k mi
06 E320 CDI "Rutherford", Black, 143k mi
91 300D "Otis", Smoke Silver, 128k mi
98 E300 "Murray", Silver, 128k mi, Stage 2 Rocketchip chip tuned, under son's care

Twelve other MB's owned and sold
2002 Honda Odyssey 241k mi (want to name it "Homer," wife won't let me)
1961 Very Tolerant Wife
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  #5  
Old 08-31-2018, 02:17 PM
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Join Date: Jul 2004
Location: Barrington, RI
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Actually here's link to test idle speed in particular:

http://www.w124performance.com/service/w124CD1/Program/Engine/602_603/07.1-2006.pdf
__________________
06 E320 CDI "Benson", Platinum Blue, 173k mi
06 E320 CDI "Rutherford", Black, 143k mi
91 300D "Otis", Smoke Silver, 128k mi
98 E300 "Murray", Silver, 128k mi, Stage 2 Rocketchip chip tuned, under son's care

Twelve other MB's owned and sold
2002 Honda Odyssey 241k mi (want to name it "Homer," wife won't let me)
1961 Very Tolerant Wife
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  #6  
Old 08-31-2018, 02:23 PM
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As mentioned above, idle speed is controlled by the EDS computer. Do you have other symptoms of problems, such as an ABS light or intermittent tach? If so, you probably have a bad or failing OVP relay.
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  #7  
Old 08-31-2018, 02:53 PM
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no other symptoms that i have noticed. No lights on the dash. tachometer solid steady.

battery voltage good. charging 13.5ish volts at around 1200 rpms
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Current fleet
1992 300D "IceBerg"
1984 300D "Blues Mobile"

1978 300CD "El Toro" Gone on to be born again
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  #8  
Old 08-31-2018, 03:10 PM
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Im with Dieseal300 OVP
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92 e300d2.5t
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  #9  
Old 08-31-2018, 03:53 PM
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Im with Dieseal300 OVP
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92 e300d2.5t
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  #10  
Old 08-31-2018, 03:55 PM
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smoke gets in your eyes
 
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Location: SF Bay Area
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Check that the connector is firmly plugged into the ELR actuator, the round thing at the back end of the IP.

Sixto
98 E320s sedan and wagon
02 C320 wagon
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  #11  
Old 08-31-2018, 05:08 PM
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Location: Carolina
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I have unplugged and plugged the wiring for the actuator a couple times. no change

can someone tell me where the resistance timing plug is located?

i will be working through the test procedure to see if i can isolate the problem.
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Current fleet
1992 300D "IceBerg"
1984 300D "Blues Mobile"

1978 300CD "El Toro" Gone on to be born again
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  #12  
Old 08-31-2018, 10:20 PM
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This may help:


https://www.yumpu.com/en/document/view/36522505/0520-adapting-ignition-timing-point-with-resistance-trimming-plug-to-
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  #13  
Old 09-01-2018, 02:12 PM
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Location: Barrington, RI
Posts: 5,416
Where is the EDS located on our cars? How would one access it?
__________________
06 E320 CDI "Benson", Platinum Blue, 173k mi
06 E320 CDI "Rutherford", Black, 143k mi
91 300D "Otis", Smoke Silver, 128k mi
98 E300 "Murray", Silver, 128k mi, Stage 2 Rocketchip chip tuned, under son's care

Twelve other MB's owned and sold
2002 Honda Odyssey 241k mi (want to name it "Homer," wife won't let me)
1961 Very Tolerant Wife
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  #14  
Old 09-01-2018, 06:31 PM
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smoke gets in your eyes
 
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Location: SF Bay Area
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Should be in the cubby behind the battery. I don’t think the 2.5 turbo has idle speed adjustment. The ‘87 300D/TD has a trim knob by the brake booster, IIRC.

Sixto
98 E320s sedan and wagon
02 C320 wagon
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  #15  
Old 09-01-2018, 10:55 PM
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If it doesn't have the round trim resistor, it will have a single rectangular trim resistor. You can change idle speed by changing the resistor.
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