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Old 01-31-2015, 09:36 PM
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So I'm in need of some tech advice with regards to my W124

forgive the Xpost from MBworld, but it seems there is quite a bit more traffic here..

Since I bought my new to me w124, Its had a bit of a rough idle, but runs and drive fantastically off idle. It surges/ pulses as if it has a vacuum leak. I picked up one of "ricks scanners" (a blink type scanner) and pulled the codes just now. In looking at how much they vary, I'm curious as to whether or not I have just a bunch of little issues, or potentially one root cause.

I have to admit, I tend to prefer Japanese made vehicles, and the w124 is almost like chinese to me. That being said, I'm a competent mechanic and really just looking for some seasoned opinions before I dive in. (also its ~ 3*F outside right now, So i'd like to spend as little time dicking around with it outside as possible )

first, A bit of info about the vehicle. It is a 1993 300E, m104, 3.2L, RWD, AT with 167k.

The codes I pulled are:

6 - 3, 5, 8 (air bag codes, not all that concerned with them ATM..)
8 - 4, 13
14 - 3, 5, 11

Which breaks down to
8-4: Load Sensor in EAL/AKR control module faulty
8-13: Full load contact does not open
14-3: Cruise control/ Idle speed control actuator
14-5: Stop lamp switch (third brake light is out, Will this set this code?)
14-11: Fuel Safety Shut off to LF-SFI control module

SRS codes
6-3: Driver Airbag Squib
6-5: Airbag/ETR, Driver seat belt buckle switch
6-8: Voltage supply interrupted

Now, I drove it to work today.. Cruise control works fantastically. To the best of my knowledge, the cruise control is a vacuum operated system on these cars, Meaning that if I had a vacuum leak.. The system wouldn't operate as intended. I suspected the idle control valve, and the EGR as possible culprits, but lack of EGR codes and a good hydrocarbon reading from the tailpipe leads me to believe that the EGR is not the culprit.

Which brings me back around to the IACV. My first step, baring all these things are not related to one lousy ground, ETC. Is to pull the little sucker and clean the hell out of it.

Thank's in advance.

Party on.
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Old 02-01-2015, 12:19 PM
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Location: California
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First, saying that the w124 is Chinese to you is blasphemy and should never even be used in the same sentence. Second, have you tested for vacuum leaks? That's where I would start. Then I would check the integrity of the plugs, wires, cap, and rotor: visually making sure they look ok. Next I would move on to check the fuel delivery. My guess would be vacuum though because if it starts fine and runs fine while driving then I don't see it being ignition or fuel, but I have been wrong before.

1990 190E 2.6L
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Old 02-01-2015, 12:31 PM
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Haha, I just meant foreign to me. I have not, what concerns me is the EAL/AKR control module/ full load contact. How could that be vacuum leak related?
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Old 02-01-2015, 12:45 PM
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It couldn't be vacuum related. Test the component, I'm not sure how you would do that though. Maybe test the resistance of it to see if it's within spec.

1990 190E 2.6L
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Old 02-01-2015, 01:22 PM
Stretch's Avatar a shield of steel
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I'd be concentrating on the load sensor errors

Here's loads of reading =>
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior

Don't leave that there - I'll take it to bits!
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Old 02-02-2015, 06:33 PM
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Originally Posted by lsmalley View Post
It couldn't be vacuum related. Test the component, I'm not sure how you would do that though. Maybe test the resistance of it to see if it's within spec.
another user PM'd me some great info. It turns out the California emissions cars use different diagnostic codes than the non Cali cars.

most of the codes are the same, but the pin 8 is different.

8-4 is a MAF code
8-13 is an o2 sensor code.

Maf's are cheap.

I think my plan of action is clean the maf, clean the IACV, test the voltage for the o2 sensor, do a static discharge and go from there.

Though the more I stare at those codes, and the more I read, I'm guessing I'll be doing intake manifold gaskets shortly. My inner mechanic says go with your gut of vacuum leak.

Last edited by 1055; 02-02-2015 at 06:44 PM.
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Old 02-02-2015, 08:46 PM
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MAFs do fail occasionally on those but it isn't super common. It is common to see the harness deteriorated and shorting out near the maf connector. Look around near the front of the engine and see what condition any other exposed harness is in before trying to clean the MAF. Cleaning wont do anything for a failing MAF and you could make the harness much worse dicking with it.
90 300TE 4-Matic

Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
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MS2E, 60-2 Direct Coil Control
3" Exhaust, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Brake Discs, .034 Booster.
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91 300CE parting

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Old 02-03-2015, 04:33 PM
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Thanks to some more info I recieved via PM, I now know how to identify the old harness vs new, so I will be checking that when I get home.

I'm still leaning towards small vacuum leak. are there common lines I should check? everything I seem to read is with regards to the older w124s with the pancake air boxes.
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Old 02-03-2015, 05:32 PM
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Bad MAF caused my C280 to surge at idle. Ran good down the road. I tried to clean it, but no help until it was replaced.
1998 C280
1982 240D Manual - Sold
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Old 02-03-2015, 11:10 PM
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can be 02 sensor
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Old 02-06-2015, 04:13 PM
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So I went out yesterday because it finally broke 25* to mess around with it.

Harness looks like its in great shape, the rubber is all in good shape, there are no brittle bits.

One thing I did notice is that where the lower intake y pipe meets the upper, both rubber boots have some oil on them from a leaking power steering line. I'm hopping it gets up to around 40* in the next few weeks so I can go out and spray it down with some carb cleaner to hopefully rule out a vacuum leak. If not, my money is on MAF. I unplugged it while the vehicle was running and it made no apparent difference to the vehicle that it was unplugged.
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Old 03-14-2015, 03:52 PM
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alright, an update. After a couple years of not being in the repair industry, I was suddenly hit with the realization of why I left yesterday. Went out in the beautiful 40* weather and pulled her out of hibernation. A few weeks ago, I had gone to clean the throttle body and was pleasantly surprised by the fact that it needed no cleaning! Although... there was quite a bit (at least an ounce or two) of oil in liquid form in the bottom of the throttle body, vixible past the throttle plate. doh! Everything is telling me this can't be good. Along with that, I discovered some leaking coolant down the side of the block and what appears to be a rear headgasket leak.

Looks like I'm enjoying the m104 through the summer before project chevybenz ensues.

Oh, you're intrigued by chevybenz? I know, I came up with the name all on my own. I'm going to perform sacrilege, and anger some pretty petty people on here. I just so happen to have a smushed up vette. The kind with the 350 and a 700r4 trans. What does this mean you may ask? that m104 and its over engineered everything is coming right on out, and the engine/trans from the 'vette is going right in.

All of my measurements check out. I know I'll have to run reverse exhaust manifolds, make some custom mounts and try and find a front sump oil pan, (or maybe Ill just cut the cross member and weld in some tube). I've seen all the stuff about cutting the firewall and yadda yadda yadda.

my biggest hurdle will be the driveshaft. I've already ordered a coilover systems with stiffer springs (thought I would like to find an upper mount bearing solution that would allow me to run a spring over coil set up.

as of right now, I'm looking for suggestions for the driveshaft. I know theres a couple people that have swapped domestic motors into their older sleds. any input would be appreciated.
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