W124 M103 300e diagnoses
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From: SoCal
2024 c300 , 2006 E55, 2005 e320, 2007 gl450, 2025 glc300, 2025 e450
W124 M103 300e diagnoses
Hey everyone, just wanted some feedback to see if I’m proceeding with fixing my 124 1990 300e M103 correctly. So recently the car started shaking a bit at idle etc now I’m not sure if it’s because I have no muffler or resonator, or because I needed to do some servicing on it outside of oil and transmission servicing. Tonite o changed the spark plugs with oem Bosch ones, not sure on the gap but I hand tightened them socket tightened, now I plan to change the wires and distributor cap, any advice on what to do alongside these services to fix the vibration?
thanks
thanks
Super Member
Joined: Jan 2015
Posts: 920
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From: Worcestershire UK
W124 260E
Problem could be due to bad HT leads distributor cap and rotor arm .Do these and forget them for the next 5 years or more . You can go with Beru parts these are fitted to a lot of mercedes engines ,Check all earth points - like chassis to engine.Remove the earth points from chassis clean it up both serfaces and give them a dab of grease ,re fit . Next is your fuse box open it up and clean each fuse ,look at it to see if any damage on the end where it coonntacts the brass fuse holders . I use a little WD 40 on the brass holders and wipe off after then refit the fuses ...Take a picture with your phone of the fuses locations because all holders are not used in the box. Take a look in the engine at night ,,,do it in the dark with ebgine running to see if you can see any flashing [short]
Thread Starter
MBWorld Fanatic!
Joined: Apr 2015
Posts: 1,421
Likes: 160
From: SoCal
2024 c300 , 2006 E55, 2005 e320, 2007 gl450, 2025 glc300, 2025 e450
Problem could be due to bad HT leads distributor cap and rotor arm .Do these and forget them for the next 5 years or more . You can go with Beru parts these are fitted to a lot of mercedes engines ,Check all earth points - like chassis to engine.Remove the earth points from chassis clean it up both serfaces and give them a dab of grease ,re fit . Next is your fuse box open it up and clean each fuse ,look at it to see if any damage on the end where it coonntacts the brass fuse holders . I use a little WD 40 on the brass holders and wipe off after then refit the fuses ...Take a picture with your phone of the fuses locations because all holders are not used in the box. Take a look in the engine at night ,,,do it in the dark with ebgine running to see if you can see any flashing [short]
Super Member
Joined: Jan 2015
Posts: 920
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From: Worcestershire UK
W124 260E
As for oil i have only ever used Castrol Magnatec but i have thought about this liquimolly .But only semi synthetic for me .The engine is 31 years old with under 100.000 on the clock. But the reason i use semi is because the car has no oil leaking at the time we speak .,, but the sem isynthetic will find every crevice it can to get out and synthtic oil will do just that. Did you have time to do the other jobs i told you about ?. Did you change the dizzy cap .
Thread Starter
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Joined: Apr 2015
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From: SoCal
2024 c300 , 2006 E55, 2005 e320, 2007 gl450, 2025 glc300, 2025 e450
As for oil i have only ever used Castrol Magnatec but i have thought about this liquimolly .But only semi synthetic for me .The engine is 31 years old with under 100.000 on the clock. But the reason i use semi is because the car has no oil leaking at the time we speak .,, but the sem isynthetic will find every crevice it can to get out and synthtic oil will do just that. Did you have time to do the other jobs i told you about ?. Did you change the dizzy cap .
Super Member
Joined: Jan 2015
Posts: 920
Likes: 46
From: Worcestershire UK
W124 260E
You never said what viscosity it is . I just go to a oil company punch in my vin number it will tell you your the right type of oil you need . Dont know the right viscosity for your car but liquimolly is a fine oil .
Thread Starter
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From: SoCal
2024 c300 , 2006 E55, 2005 e320, 2007 gl450, 2025 glc300, 2025 e450
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Senior Member
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Just stand clear of the body of the car and while idling (shaking), pull off each plug wire until you find the one that doesn't make much difference. This cylinder is your misfire. Then check the plug wire resistance with an ohm meter(cheap) and it should be what's marked on the resistor end of the plug wire. Probably 1K ohms. Start there to see if it's a bad resistor end or possible dirty injector, injector cup seal leak.
A consistent misfire should be easy to find.
A consistent misfire should be easy to find.
Super Member
Joined: Jan 2015
Posts: 920
Likes: 46
From: Worcestershire UK
W124 260E
Tool;s are on ebay that you put on to the ht lead ,so that you can see it flashing as it fires ,or use an old strobe timing light . Get all the electric ht side up tp scratch .And i bet your problems go away . I have had this missing problem on 2 of my mercs this one i have now the w124 and my w123 i had before it .And each time its been one of the ht leads going down . The set i removed i keep , along with distributor cap and the rotor arm. They were 31 years old and never missed a beat ,but i must say it did start missing last year and i had to replace just one ht lead on the 6 cylinder ,, but after so long they could pack up at any time so thought it best to change them all .I had the cash anf it was burning a hole in my pocket ha ha ..so replaced the whole ht side with a new set of Beru plugs to go with them.
