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  #1  
Old 08-07-2002, 11:32 PM
thevilla
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'93 300e idle surging - fault code 009...advice needed

hello,

i just purchased a 1993 300e with 67,000 miles. an excellent driver but has a surge at idle ranging from 500-1100 rpm. i scanned the ecu and am getting a 009 hfm signal too high code.
my pockets are not deep enough to throw parts at it so am i looking for advice to further diagnose the issue. any comments appreciated!

thanks in advance,
rob
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  #2  
Old 08-08-2002, 12:18 AM
amg280's Avatar
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Join Date: Apr 2002
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I believe that would indicate a faulty Air Mass Meter (hot film meter). You can find used ones for around 100 bucks. Dont quote me on this, it could be wiring going to it, or maybe something entirely different.

Good luck.
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  #3  
Old 08-08-2002, 12:23 AM
pmizell's Avatar
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I show code 9 as being -- intake air temp sensor-open or short circuit-- not sure if this is the same as what amg280 describes or not. Check the sensor to make sure it is plugged in securely.

http://www.batauto.com/MB/

Good luck!
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  #4  
Old 08-08-2002, 12:40 AM
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I have a 1993 300E and had a surging idle similar to what you are describing.

Common causes of this sympton usually are:

1. mass air flow meter
2. vacuum leak
3. throttle actuator

My problem in the end turned out to be a vacuum leak at the intake manifold. My crack mechanic figured this out after changing a $961 actuator and a $250 mass air meter.
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2001 E430, Bourdeaux Red, Oyster interior.
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1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
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  #5  
Old 08-08-2002, 12:41 AM
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One more thing - does your cruise control work?

Another symptom of a bad throttle actuator is a mal-functioning cruise control.

Our wonderful German engineers designed 3 or 4 separate functions into the actuator. If any of these go out, you're replacing a $1,000 part.
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2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
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  #6  
Old 08-08-2002, 07:39 AM
engatwork's Avatar
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For reference in the future I would suggest, on a good running car, to disconnect a vacuum line at idle and watch how the car runs/idles. Try disconnecting a small one and a large one. Disconnecting a large one will make the engine run REAL rough whereas the small ones are not quite as bad but do show up. Also, if you want to get real adventursome disconnect the MAS meter and watch the idle.

I recently resolved a very, very slight "miss" at idle on my E320 and found that I had the plugs gapped too close together.
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Last edited by engatwork; 08-08-2002 at 01:15 PM.
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  #7  
Old 08-08-2002, 08:49 AM
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Location: Florida / N.H.
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Do as Paul said..
The Intake Air Sensor is located on the driver side of the intake cross pipe.
They usually forget to plug them back in when sevicing the car..
If it is plugged in, then unplug it and test it w/ohm meter.
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  #8  
Old 08-08-2002, 09:55 AM
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Hi Rob,

I get heated O2 sensor open circuit for code 9 HFM-SFI. The DM gives Air temp sensor for its code 9. The airtemp sensor won't cause the surging. The O2 sensor probably won't either although the code could be an indication of a vacuum leak or AMM problem (if the code 9 was on the HFM).

I'm thinkin that I drove your car yesterday and taking off I was in some rain water and your traction control took over. This would indicate that you have EA/CC/ISC instead of just CC/ISC. It would be interesting to see the codes on that module also. This would be on pin 14 of the test connector.
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  #9  
Old 08-08-2002, 10:10 AM
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SB is on the right track..
I was assuming [that never works] a code 9 on DM. BUT,
You have a HHT 009 code on the HFM module, which is , as you already know, MAF sensor problem..
Might want to check the boot clamp at the intake before anything

This would also be a flash code 4 on pin 8 [HFM mod.}

Am I with you now?
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  #10  
Old 08-12-2002, 09:25 PM
thevilla
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thanks to all for the responses to my problem. i initially scanned the other sockets with the following results:

7) code 13-ect open circuit
8) code 009 amm signal too high
14) codes 112-can:fault in transmission from efp n4/1
182-safety fuel shut-off switch signal n3/1
224-idle speed contact switch s29/3

i have also since discovered that i have the dreaded wiring harness insulation flaking syndrome. the good news is that my local dealer agreed to do it for 2.5 hours labor and no parts cost. i hope this cures my ills but with the number of faults stored, this may not be the case. i will report back after the harness replacement later in the week. btw, thanks stevebfl for your assistance and the alignment gave the vehicle a better "feel".

best regards,
rob

Last edited by thevilla; 08-12-2002 at 10:57 PM.
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  #11  
Old 08-16-2002, 09:55 PM
thevilla
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follow-up report

hello all,

i had the harness replaced two days ago having to pay only labor as the dealer goodwilled the part. the engine still exhibited the intermittent rough idle, surge, and hesitation. also, i rechecked the system for faults and the 009 hfm was still present. i replaced the amm today and am amazed at the performance i was missing! having only had the car for two weeks and it being my first w124, i think i'll keep this one for awhile. thanks again to all that replied.

best regards,
rob
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  #12  
Old 12-08-2002, 10:18 AM
est est is offline
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Location: Tallinn, Estonia
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Unhappy

Please don't judge me harshly if i did not comepletely understand the wiring harness part.
I have a problem with fluctuating idle on 124032( e320 hfm-sfi)
Idle speed rises from 500 to 1100 intermittently in P/N. The interesting part is that no faults are detected, but disconecting the airflow meter seems to make the problem go away. I replaced the airflow meter from a car with no such problems, but after a while idle is surging again. Wiring harness?
I also monitored the signal coming out of amm: if the signal wire(disconnected) voltage is measured against ground while the other wires are connected- signal is beatyful. If the signal wire is connected- my Bosch PMS shows voltage surges when the fluctuation stars.
Or should i look for vacuum leaks, dirty isc, faulty output from transmission?
Thanks ahead - est
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  #13  
Old 12-09-2002, 07:56 PM
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Disconnecting the airflow sensor will of course put you in open-loop 'limp' mode, which will probably be a pretty steady idle. Mixture will be off, but if properly adjusted, probably not a lot - but enough to fail emissions.

Anyway, I would first look for air leaks in the idle circuit, anything that will prevent the airflow meter from properly gauging that parameter.

Steve
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  #14  
Old 12-10-2002, 04:27 AM
est est is offline
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Thanks.
I am very well aware that the leaks can cause this problem, and my first guess was that the tank ventilation valve is stuck, but replacing it did not do it. Also, one by one, i took every vacuum hose off the manifold and plugged them up- did not help either.
ISC was taken apart and checked- everything looked very well. This car does not have the 14th pin in the diagnostic socket
The idle got even worse over a week. Now the fluctuations are in every mode - driving in traffic, reversing, parking. Also the CU gives me the " airflow mass sensor signal- voltage too high" constantly. I checked for the short circuits in wiring and found none. New air flow meter is ordered so i will have to wait and see what happens. Any comments and advice are very, very welcomed.
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  #15  
Old 12-10-2002, 02:34 PM
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I will be watching your thread closely, as I am dealing with the EXACT same issue on my W124.

Idle surge for the last two years, and has gotten worse. Also sometimes stalling out when starting cold and putting in gear.

Balking on ordering the part just yet, so I will see what results you achieve...
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