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  #1  
Old 11-18-2012, 04:05 PM
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Location: Midwest
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400E rough start/idle when cold

Proud owner of a 92 400E with 180,000 miles.
About 1 month ago my cruise control stopped working, about a week later a rough idle at cold start began. The rough idle has become progresivly worse over the last few weeks to the point where the car will start and instantly die.
Here is what I have done so far:

In the mornings (cold start) I have to keep the rpm's up for a few mins until warm then the idle drops down below 500 and almost dies. I am noticing vibration coming from drivers side of engine compartment until engine is fully warmed up. I also see a distinct loss of power during the cold start, dim lights, slow to pick up speed and almost stalls. After car is warm it starts and drives like normal apart from a slightly rough idle.

Replaced plugs, distibutor caps & rotors. After I did the caps and rotors she started up normally but then the following day was back to the bad symptoms.

I looked around the forums but could not seem to pinpoint a thread to help rectify this problem so any help would be greatly appreciated. Also I am by no means an experienced mechanic, but can handle the basics and willing to learn new things.

All the best,
Luke H

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  #2  
Old 11-18-2012, 04:19 PM
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Your cruise control is effectuated through your Electronic Throttle Actuator (ETA). I had a 93 400E where the cruise control stopped working and it turned out to be a bad ETA cable (they used the same bogus wiring on the ETA as on the wiring harness). The insulation on the wires inside the ETA cable crumbles and the wires short out. I discovered this by accident because I moved the ETA cable slightly and noticed the cruise control started working again.

Another function of the ETA is Idle Speed Control. I would start with the ETA and cable. Also, if the upper engine wiring harness is original, it probably needs to be replaced. On the 92 model, you probably have the 90 degree angle connector for the ETA. I think they went to a straight connector in late 93 or early 94. Mercedes sells the cable for the old style and, if you are good at soldering, you can change the cable yourself. You have to special order the cable. Most dealers don't carry the part.
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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles
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  #3  
Old 11-19-2012, 10:20 PM
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Thank you for the great info.
This could explain why my problems vanished after the cap/rotor install, then came back all too soon the next day.
I will take a look under my hood and post some follow ups, now I am a little scared what I might find under there after doing some research on the problematic ETA/wiring harness.
Any ballpark idea on costs for the parts & any sources?

Thanks,
Luke
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  #4  
Old 11-19-2012, 10:37 PM
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You can have the ETA rebuilt with a 2-year warranty for about $275 through Don Roden Electronics in AL. The wiring harness can be purchased for around $500-600 and it doesn't take more than about an hour or two to install with no special tools. If you are planning to keep the car and the wiring harness is original, I would definitely change that. Usually the ETA's with ASR are more problematic. I don't know if your car had that option. My old 93 400E did not, but the harness for the ETA was still toast.

By the way, I accidentally discovered my ETA cable was bad when I was looking under the hood with the ignition on and the engine off. I was trying to figure out why my cruise control had stopped working. I was leaning on top of the air filter housing and it pressed down onto the bad ETA cable and caused the ETA motor to actuate. I discovered that every time I pushed on the housing the electric motor would run. Eventually I traced it back to the ETA cable underneath. Then I realized that I could get my cruise control to work, or stop working, by moving the cable in different positions.

The ETA is not hard to remove. It sits right under the mass air flow sensor or LH (hot wire) as Mercedes calls it. You will likely have to replace the hardened hose that goes from the back of the passenger side valve cover across the engine to the ETA. It comes in sections and it is difficult to replace just one section without breaking the next. You will see what I am talking about once you get the air filter housing off. The hose is #29 in the diagram. http://www.w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Engine/119/30-1262E.pdf
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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles

Last edited by emerydc8; 11-20-2012 at 02:51 AM.
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  #5  
Old 11-24-2012, 10:35 AM
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Great follow up! thanks for the link to the PDF and rebuild source.
My 400 does not have the ASR option & I have not had a chance to get under the hood yet but will post once I do. If I do end I doing the rebuild, I will be sure to have the new hose sections ready in case anything breaks.

Luke
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  #6  
Old 12-04-2012, 09:32 PM
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Bad news update

I drove the car to work today (approx 5 miles) and the car stalled, the ABS and SRS lights came on then she started up again with me forcing the rpms. After sitting for the work day the car would not start. So there it sits in the parking garage downtown for the night. I have not had a chance to get under the hood and inspect the ETA wiring and have continued driving the car since my first post. The car was making a whining noise from the engine bay this morning and the rev needle was displaying much higher than actual revs on the engine.

When I tried to start the car after wk all I got was the buzzer noise (weak) from key in the ignition then ABS & SRS lights come on (weak glow) & the buzzer continues until I remove the key. No other electronics are working.
Any ideas?
Am I looking at a tow to get it home?
Thanks again,
Luke
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  #7  
Old 12-05-2012, 12:48 AM
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Location: Arizona
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I have not experienced this personally, but I have read that a low battery or low voltage output from the charging system will cause ASR and ABS problems. You could throw in a new battery or a newly-charged battery and see what happens. Maybe the whining noise is a bad alternator.
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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles
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  #8  
Old 12-06-2012, 12:32 AM
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Quote:
Originally Posted by emerydc8 View Post
You can have the ETA rebuilt with a 2-year warranty for about $275 through Don Roden Electronics in AL. The wiring harness can be purchased for around $500-600 and it doesn't take more than about an hour or two to install with no special tools. If you are planning to keep the car and the wiring harness is original, I would definitely change that. Usually the ETA's with ASR are more problematic. I don't know if your car had that option. My old 93 400E did not, but the harness for the ETA was still toast.

By the way, I accidentally discovered my ETA cable was bad when I was looking under the hood with the ignition on and the engine off. I was trying to figure out why my cruise control had stopped working. I was leaning on top of the air filter housing and it pressed down onto the bad ETA cable and caused the ETA motor to actuate. I discovered that every time I pushed on the housing the electric motor would run. Eventually I traced it back to the ETA cable underneath. Then I realized that I could get my cruise control to work, or stop working, by moving the cable in different positions.

The ETA is not hard to remove. It sits right under the mass air flow sensor or LH (hot wire) as Mercedes calls it. You will likely have to replace the hardened hose that goes from the back of the passenger side valve cover across the engine to the ETA. It comes in sections and it is difficult to replace just one section without breaking the next. You will see what I am talking about once you get the air filter housing off. The hose is #29 in the diagram. http://www.w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Engine/119/30-1262E.pdf

Hi,

Thanks for the post above. I added bold text to one part of particular interest. I have a 400e that was diagnosed with a failing wiring harness. The symptoms match some of what has been mentioned above .

I found a replacement harness in the price range you mentioned but have not found a diagram or video of where the harness fits on the car. Is the harness replacement fairly self-evident? How much needs to be removed to do this replacement. Do you (or anyone) know of a guide that shows the harness?

Thanks!
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  #9  
Old 12-06-2012, 01:50 AM
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You can change the wiring harness on the 400E in the parking lot in about an hour. It is really easy. You have to take the air filter housing off and you will see it. The hardest part is where the lever-type rectangular plug goes through the hole in the firewall towards the back passenger side of the engine compartment, but that's not even too bad.

All you need is an Allen wrench set and a screw driver. If I recall correctly, there are 8 fuel injection plugs, a plug for the mass air flow sensor, one for each cam sensor on the front of the engine, one for the coolant temperature sensor on the front intake manifold and maybe one or two others. It is really intuitive once you lay the new harness along the old one.

If you search wiring harness and 400E or E420, you should find more information if you need it. Here's my post from years ago and some of the issues I ran into. 400E wiring harness update
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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles
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  #10  
Old 12-06-2012, 09:10 AM
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Thanks for the quick reply and also for the details!

The dealer quoted well over $2K for the p&l.

Your description makes the job sound very straight forward.

When you were doing the job, were any of the places the harness connects to degraded or very degraded? I guess I’m asking if other parts may need to be swapped at the time the harness is done?
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  #11  
Old 12-06-2012, 10:07 AM
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If I recall, it was the rubber elbow that attaches to the aft passenger side valve cover that was in the way of sliding the harness connector through the firewall. I ended up having to run the wires through from the back of the wall because I couldn't move the hose and didn't have a replacement hose at the time. So, it wouldn't be a bad idea to order that hose.

Other than that, just be careful not to disturb the ETA wire harness running across the top of the engine, just in case it's in bad shape too. You'll see what I'm talking about when you get the air filter housing off.
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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles
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  #12  
Old 12-12-2012, 09:17 AM
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Follow up

So the car battery ended up being totally flat. I charged the bat and the car turned over and died. Managed to drive it to my cousins shop where we opened up some of the upper harness and ETA harness, both were in very bad shape. I'm pretty sure everyone has seen the pictures so I will spare you those. Also if left connected something is drawing a charge on the battery till it is completely flat. Dealer quoted me $750 for a new wiring harness, anyone have a cheaper source? Anyone had any luck with eBay purchases? There are currently a few on there for under $350.
Currently the car is sitting in the garage looking very sad and I would love to get rolling again!
Thanks again,
Luke
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  #13  
Old 12-14-2012, 09:49 AM
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Dishonest dealer

Emerydc8 thanks for the PM!
I called my local dealer yesterday just to see what they would quote. Got a helpful guy from parts who offered the upper harness at a "goodwill" price of $610 versus $755 retail. I ordered the part through them but declined the 8 hours service they quoted. I was shocked, 8hrs, this is a f@$kin joke!
Hopefully I can get the new harness in soon
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  #14  
Old 12-14-2012, 01:41 PM
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8 hrs might be standard dealer book time on that job...it's really only a 1-2 hour job for a tech who has done it before and works at it w/o a break, 2-3 if you never did it before...something like 17 connectors is all there is. Lay the new one on top or next to the old one and un-plug/plug 1 connector at a time. Easy.

But yes, 8 hrs is crazy ! Especailly at $100+ an hour at a MB dealer. But hey, they have all that overhead to cover right?
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  #15  
Old 12-19-2012, 10:22 AM
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The new harness is in, but all symptoms are still present. I proceeded to remove the MAF to get the ETA out for a rebuild. While working in that area the small white tube snapped and I have about a 12" section that broke loose. I can see where it attaches at the top of the engine but not where it attaches at the other end. What is the purpose of this tube?, venting? And does it attach at both ends?
Thanks,
Luke

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