Originally Posted by alynch

Low and middle rpm stumbling combined with brake issues would seem to point to a vacuum leak somewhere. Vacuum issues have less of an effect at high rpms.

Originally Posted by azblk

I had to make the same decision at the beginning of 2019 and I decided to try and save the engine - that had gone a little bit over 50K miles without an oil change. It took me about a month and a half to complete the job from start to finish - working on it in my spare time never longer than 2 or 3 hours a week. The job was pretty straight forward if you are somewhat mechanically inclined. The total cost was something like $1500 parts/tools as I was able to clean and reuse almost all the original parts. Its been 10.5K miles since the repair and the car has been running flawlessly - so i can say I succeeded.

The simplest solution would have been to buy a used engine from a wrecking yard and put that in but I figured since it was already "broken" I might as well give it a shot as I could not make it worse.

What I would tell you is do the tear down to block, inspect all the parts for wear and tear, warpage, scoring and the like. By the time you get to the pistons you should know whether it is worth your time and money attempting the rebuild.

My rule of thumb was since it was running before i started the teardown then it has to run after I rebuild it as long as I do everything correctly.

Originally Posted by kbod

So This morning I went on a drive. Lots of smoke at start up and no smoke there after. Car has a really bad misfire at idle and at 2500-3200 rpm. After it runs fine but the car is definitely low on power. The brakes are still rock solid with no assist but I just pushed really hard on them and the car would stop. I cant see any noticeable vacuum leaks under the hood but when I disconnected the brake booster with the engine running the suction on the hose was weak and I barely felt anything at all sucking in and also the idle didn't change at all and it was still idling badly. Is it possible the entire cause of the oil smoke and bad brakes and vacuum leak this entire time was the vacuum pump?

Originally Posted by azblk

Your smoking problem is coming from oil leaking into the cylinders through valve stem seals. I happens at startup mostly because when the engine is not running the oil lubricating the cam/lifters/cans starts to settle at bottom of head and will find its way into the cylinders due to the leaking seals. When the engine starts running less and less oil makes it into the cylinders and you get less or no smoke. When you turn off the engine the cycle repeats and you get smoke on start up.

Vacuum pump only affects brakes - would not cause your idling problem.

Is the car throwing any codes? if it is what codes?

Originally Posted by kbod

the car is throwing cylinder 2 and 3 missfire codes along with an engine reduced power program code. The car idles really rough and low, when accelerating it jitters and stutters and missfires at 2-3000 rpm ALOT and thereafter it revs to redline just fine. The brakes work but there is no assist at all, Pulling the hose off the brake booster I noticed the suction is extremely little at idle. Taking off from a stand still is really hard and it feels like the car is in some sort of limp mode. When in drive or especially reverse while backing up slowly with the steering wheel turned the engine missfires so badly and runs so rough the entire car shakes terribly.

Originally Posted by azblk

You try swapping the coils from 2 and 3 with 1 and 4. If the misfire follows the coils then you have bad coils on 2 and 3. Any bad misfire/idle can put the car in limp node

Originally Posted by kbod

spark plugs were replaced and ignition coils were all swapped around.
no change to report

Originally Posted by azblk

Pull the coils again. Make sure you have no oil leaking into the plug wells and that coils are perfectly dry. If those check out then pull valve cover and check your timing chain and valve timing. The chain tensioner on this engine is hydraulic- so it can fail too due to lack of oil changes and the timing chain could have jumped a tooth or two.

If your timing is good it means chain and tensioner are also good.

Originally Posted by kbod

Ok so I cleared my codes and went on a 70 mile drive. The only code that came back was a cylinder 2 missfire. swapped cylinder 2 with 3 coils, Code became a cylinder 3 misfire. I ordered a new ignition coil. The vaccum pump is dedicated for the power brakes and my power brakes don't work. I ordered a new vacuum pump. Last night I gave it another oil change. In less than 100 miles the new oil and flush became DARK and ruined, and the brand new filter was now disgusting and all the filter was full of sludge chunkies. Not great, but clearly the engine is getting cleaner so no complaints there. I put new oil, more flush, and a new filter. I plan on doing that at least one more time. This leaves me with the last issue. The oil smoke. the car isnt nearly as bad as it used to be. But about 1 or 2 minutes after turning it on it will put out lots of burnt oil, and then after warming up it will not smoke at all, especially when accelerating. but even when the engine is hot at idle it might give a little smoke. does that sound like valve seals? not sure. But I want to fix that oil burning issue as its probably ruining my emissions system, and its embarrassing.

Originally Posted by azblk

There is only 2 ways for oil to get into your cylinders. One is through the stem seals and another through the piston rings. You can rule out the rings by doing a either a compression or a leak down test. If that fails - you have to pull the engine to fix or replace it. If it passes then it is definitely the valve seals that are leaking as there is no other way for oil to get in the combustion chamber.

Originally Posted by kbod

For the little oil smoke i assume keep drivin it?

Originally Posted by azblk

I don't think the smoke will go away on its own. If the smoke does not bother you and the car passes emissions then I guess you can keep driving it. Not sure what the long term implications of driving the car with leaking seals are but I assume the seals will continue to deteriorate and the problem will get worse.

Originally Posted by azblk

I don't think the smoke will go away on its own. If the smoke does not bother you and the car passes emissions then I guess you can keep driving it. Not sure what the long term implications of driving the car with leaking seals are but I assume the seals will continue to deteriorate and the problem will get worse.

Originally Posted by azblk

I don't think the smoke will go away on its own. If the smoke does not bother you and the car passes emissions then I guess you can keep driving it. Not sure what the long term implications of driving the car with leaking seals are but I assume the seals will continue to deteriorate and the problem will get worse.

Originally Posted by kbod

I changed the brake vacuum pump. I got my power brakes back. success, and after filling the tank getting the car to recreate the any problems didn't work, No check engine light or anything.. So at this point everything about the car is a clean sorted mercedes except the smoke, Heres the thing about that smoke. it only smokes 2-4 minutes after a cold start. never on a warm start and never immediately after starting. After I cold start the car at the 2nd stoplight ill look at my rear view mirror and see a CLOUD of smoke. After i hit the gas pedal tho its over. this raises my question. It can be piston rings or valve seals that introduce oil into the engine directly, But Can it be the Turbocharger? It just doesn't make sense how the oil seals would be so specific with their leakage.

Originally Posted by azblk

What you describe is classic leaking valve seals. If it was the turbo you would see smoke only at startup for 30 secs and it would be white smoke. I also do not think it is the rings and you can easily check that with a compression or leak down test.

Originally Posted by kbod

Do you know of any guide or vmanual available for the job?