Hi guys, I have this nice 1992 300E that I acquired about one and a half months and I already put 1,500 miles on it. I just noticed it last night when I came home from the shop after engine mounts replacement (Corteco) that when I put my car to Neutral or Park, the engine shakes continuously. My transmission mount is still okay (almost new according to the mechanic) so it was not replaced. But when I put the car in gear (D or R), it's very smooth. The previous owner claimed he replaced he spark plugs and wires. Any similar experience? Please advise. Thank you.

the symptoms you just described are classic bad motor mount symptoms. I had that same issue on 2 other MBs (Diesels). Maybe they were installed incorrectly.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

Thanks for the reply. I brought it back to the shop and the mechanic checked it. He said it's properly installed. I remember though that I was experiencing this shaking before. That is why I thought replacing the mounts will solve the problem. Then I was surprised last night when I saw the original mounts with 152k miles on it were still intact and no signs of cracking or leaking. Anyway, today I replaced all the spark plugs and the shaking is still present. The oils pressure gauge also bounces together with the shaking. It is funny because the shaking happens at Park or Neutral, not on gear which is common problem to older cars.

Classic engine mount symptoms.

Do a thorough tuneup first if you've already changed them

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'O=00=O'
bmw 2002.
long live the legend

Check your upper as well as lower engine wire harnesses. If these have been changed that's good. Is the car a bit hard to start warm.

I removed the Idle Control Valve to clean last night and but it was clean. But still I sprayed it with carb cleaner. I checked all the hoses of the vacuum lines and everything 's intact with no crack. I remember what the previous owner said to me that he serviced the CIS injection system. Replaced all the seals with dealer parts only. Even the injectors are new. He gave me all the receipts to confirm all his claims. I'm thinking now it could be the voltage regulator (according to Kent of **************) but I have no flickering ABS light. Or it could be a distributor cap and rotor. I'm afraid though that I will keep throwing parts on it and the problem is still there.

Do I also have a biodegradable wiring harness? I thought that started at 1993 w124.

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2015 Toyota Rav4 XLE
2014 Toyota Camry LE
2011 Mercedes C300 4 MATIC
1992 Mercedes 300E (Sunday Car)

A few things. A gas engine car with torn mounts won't shake. You have an engine smoothness problem. ( diesels with low cylinder counts amd torn mounts can shake due to their inherent roughness )

When in gear there is a load on the engine and that is likely smoothing things out. And, the idle speed goes down as well taking the engine out of the RPM range where it shakes.

Exactly! What could be the problem? It has the similar shaking of my 2011 C300 (M272) when I start in the morning. Though in my W204, shaking disappears after a minute. Complained about it before and the MB SA said it is normal. I hope this is not normal with M103 so I could fix it.

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2015 Toyota Rav4 XLE
2014 Toyota Camry LE
2011 Mercedes C300 4 MATIC
1992 Mercedes 300E (Sunday Car)

Remote diagnosis is difficult. I have two M104 cars ( The 24 valve version of your M103 ) and they are clock work smooth. However they are 97 C280 and SL320 with a very developed fuel injection system. The 280 has smoother idle due to a shorter stroke.

Does you engine have full electronic injection or CIS-E ( electronic control of a mechanical fuel injection system ) ? Full electronic injection will have a ~ 3/4" diameter tube running the length of the engine that the injectors will plug into and each injector will have a wire running to it. CIS will have a 1/8" diameter steel tube running to each injector, the other end of the tube will go to a fuel distributor.

I don't have much hands on with the CIS system and anything I have was scattered across a few different makes with a bit of time on my 91 300SL parts car. There are some threads here dealing with CIS issues. This would probably be a good thread to start though I haven't read it. Duty Cycle stuck on 90% - 89 300SEL

The M103 engine should still have an ignition distributor and these tend to have issues with arcing under the cap.

I understand what you mean. I had a 1997 C280 Sport with M104 engine and 722.6 tranny with 245k miles that I sold last April. That engine was smooth even with high miles on it. Did a compression test on it and still got 190psi on all cylinders, very durable. Loved that car especially it has no biodegradable wire harness, except the wires inside the headlights that burnt the fuse so I replaced them.

I believe my 92 300E has CIS that has a tubes to the injector from the fuel distributor. They said the M103 engine is not really that smooth. Nex week I will order the distributor, rotor. Spark plug wires only has 35k miles on it, I don't know the lifespan of the wires.

Thank you for the link. I will start reading it. I really appreciate your help.

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2015 Toyota Rav4 XLE
2014 Toyota Camry LE
2011 Mercedes C300 4 MATIC
1992 Mercedes 300E (Sunday Car)

LexBenz, remove the distributor cap and check the condition of the terminals and the end of the distributor rotor. Clean the terminals if there are deposits on them, same for the end of the distributor rotor. As previously mentioned, inspect for signs of arcing, or cracking inside the distributor cap. Replace, as/if required. Cheap ignition wires could be problematic right out of the box. Beru or Bosch make quality ignition wires.

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Fred Hoelzle

Like post above , cap rota and leeds . If mine starts doing this, it is what i would do asap.