To replace or not replace (lower harness)
Thread Starter
Junior Member
Joined: Oct 2004
Posts: 16
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From: Atlanta
95 SL500, 05 CL600, 91 RR County, 99 RR 4.6 HSE, 09 RR Autobiography, 13 RR Autobiography
To replace or not replace (lower harness)
Recently my '93 400E (128K) started loosing power while accelerating when fully warmed up. The next thing was very rough idling at all temperature ranges.
I replaced ignition cables, plugs, rotors and distributor caps. No effect!
Then replaced the upper engine harness (the one connecting injectors, etc). This fixed the rough idling problem, but the loss of power during acceleration persists although not as serious as before. The car is almost driveable.
I'd like to avoid replacing the lower harness if possible. Does anyone have any suggestion what else could be causing this?
Alex
I replaced ignition cables, plugs, rotors and distributor caps. No effect!
Then replaced the upper engine harness (the one connecting injectors, etc). This fixed the rough idling problem, but the loss of power during acceleration persists although not as serious as before. The car is almost driveable.
I'd like to avoid replacing the lower harness if possible. Does anyone have any suggestion what else could be causing this?
Alex
MBWorld Fanatic!
Joined: Feb 2002
Posts: 1,311
Likes: 11
From: Manchester, CT
Why not replace the starter/alt harness? ...they also go bad; especially at that mileage with that engine.The lower harness is much cheaper than that upper one was...but harder to install.
Any check engine light on or codes pulled? Your loss of power might not be wire related, but it also might be...need more info.
Try posting this over at Mercedesshop.com in the Tech section. Some real good techs there to help.
Any check engine light on or codes pulled? Your loss of power might not be wire related, but it also might be...need more info.
Try posting this over at Mercedesshop.com in the Tech section. Some real good techs there to help.
Thread Starter
Junior Member
Joined: Oct 2004
Posts: 16
Likes: 0
From: Atlanta
95 SL500, 05 CL600, 91 RR County, 99 RR 4.6 HSE, 09 RR Autobiography, 13 RR Autobiography
No check engine light. Don't have any codes at this time. It runs quite nicely as long as I press the accelerator very, very lightly. After a while it will reach 70-80mph and keep on going. But if I just try to press a little harder feels like I'm hitting the brakes. Then a few seconds later all cylinders start firing and it leaps forward. In neutral, it will rev to 6K with no problems.
Newbie
Joined: Apr 2004
Posts: 14
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From: Chennai, India
Mercedes Benz E220
I have a 96 E220 (HFM fuel injection system), which too had wiring harness problems. Check https://mbworld.org/forums/e-class-w124/86731-e220-hesitates-shudders-while-accelerating.html
wherein, I have described the behavior, seems similar to what you are going through. If you suspect mis-firing (such as cylinders cutting out), then it could possibly be ignition coils. If not, it could very well be the throttle body (was so in my case). Most cars that suffer wiring harness issues end up having throttle body failures. Hard to diagnose with shop computers, look for fault codes that read "false air". That may or may not show up. I don't know what sort of fuel injection system your car has. Mine has an electronic idle control unit mounted on the throttle body which is prone to failure, because of bad wiring.
If the wiring harness looks bad, change it at once, don't wait for symptoms. They usually take a few components with them when they go South.
wherein, I have described the behavior, seems similar to what you are going through. If you suspect mis-firing (such as cylinders cutting out), then it could possibly be ignition coils. If not, it could very well be the throttle body (was so in my case). Most cars that suffer wiring harness issues end up having throttle body failures. Hard to diagnose with shop computers, look for fault codes that read "false air". That may or may not show up. I don't know what sort of fuel injection system your car has. Mine has an electronic idle control unit mounted on the throttle body which is prone to failure, because of bad wiring.
If the wiring harness looks bad, change it at once, don't wait for symptoms. They usually take a few components with them when they go South.
