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  #1  
Old 03-17-2009, 10:26 PM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 5,038
Adjusting Fuel Mixture (Problem with checking idle duty cycle)

Hey everyone,

I have, for a few days anyway, an Aglient oscilloscope, so i thought I would look at my fuel mixture on my m103. Turns out it was not right.

I'll post up the measurements later, I was pretty close to getting it to spec when I lost any reading @ idle after 30 second from start...

My scope shows nothing but noise..

When you rev the engine to ~1000rpm, I hear a vacuum valve pop open/closed (seems to be connected to a pot of some sort behind the headlamp and the intake manifold) and the waveform comes back to life.

I checked the o2 sensor and its fine. fluctuating voltages.

Anyone have any clue as to why i would get no duty cycle reading from the x11 (pin2 +,pin3 -) port @ idle?

Thanks,

Kris
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82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
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93 300E 195k

Last edited by JamesDean; 03-18-2009 at 02:21 AM.
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  #2  
Old 03-18-2009, 09:17 AM
slk230red's Avatar
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Join Date: Jul 2006
Location: Tampa, FL
Posts: 820
Your '93 has to be put into 'Diagnostic Mode' to read duty cycle.
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  #3  
Old 03-18-2009, 12:32 PM
JamesDean's Avatar
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Join Date: Apr 2005
Location: NE Ohio
Posts: 5,038
Quote:
Originally Posted by slk230red View Post
Your '93 has to be put into 'Diagnostic Mode' to read duty cycle.
really? it was reading duty cycle fine up until that point...how does one enter it into diag mode? i over adjusted lambda took it up to my shop they corrected it for me... havent had a chance to look at it w scope yet..
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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #4  
Old 03-18-2009, 01:35 PM
slk230red's Avatar
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Join Date: Jul 2006
Location: Tampa, FL
Posts: 820
From the manual:

"@1988 California and
@1991 with diagnostic trouble code
storage:
The CFI control module must be switched over
to output of on/off ratio because the signal for
the diagnostic trouble code (DTC) display is
output as priority.
The output of the on/off ratio is performed once
all the DTCs have been read out and the start
button of the impulse counter scan tool or the
non-locking switch on the diagnostic connector
(California version only) is then once again
pressed (see section m).
The % readout now fluctuates when the engine
is running at normal operating temperature and
there are no DTCs."

I built a homemade LED Tester to put my '93 190E into diagnostic mode to read duty cycle. It also reads DTC's.
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2001 SLK230
1971 LS5 (454) Corvette Convertible
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  #5  
Old 03-18-2009, 04:08 PM
JamesDean's Avatar
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Join Date: Apr 2005
Location: NE Ohio
Posts: 5,038
If i have to put it in diagnostic mode to read duty cycle..what is it outputting to my scope throu x11/2 x11/3 ?


taken before any adjustment were done. all i did was connect up to x11
http://i98.photobucket.com/albums/l250/MafiaNicky/idleafterafewminutes.jpg


If it is in normal mode..why would it output anything at all?
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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #6  
Old 03-18-2009, 05:30 PM
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Posts: 247
Was that at idle?
From the looks on that waveform, it looks like a lean mixture. My 2 cents!
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  #7  
Old 03-19-2009, 07:19 PM
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Posts: 247
It's $80 but worth it for occasional use. A professional version will be much higher $$
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  #8  
Old 03-19-2009, 08:46 PM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 5,038
Checked current flow in the EHA:

(note: my motor is a m103 3L from a 90 300SEL)
(note: my exhaust is straight pipe)

Resistance: 1.116 M Ohm

Key on, Engine Cold: 19.980mA

Key on, Engine On Cold: 4.819mA

After sitting to ~80C : 16.477 mA

As engine was revved it typically went between 4 and 16mA

As engine was held @ higher rpm started @ high number and decresed rapidly to around two or three mA.

Used this: http://www.home.agilent.com/agilent/product.jspx?pn=34410A
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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #9  
Old 03-20-2009, 12:17 AM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 5,038
just filled up at the gas station

11.02 gallons covered 212 miles....for 19.36 Mpg..
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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