FM099

Good evening, dear users.

I have been trying to fix my car's problem nearly three months. However, It does not fix. I will really appreciate who helps me about my problem.

I have a misfire when it is in cold engine/start. However, when I am waiting to the engine's temperature comes to the 90 degree, i turned off car and then turn on it fixed the misfire. When it is in the current mod of the misfiring, when i am pushing the gas pedal, the car does not feel the gas pedal. It shows the problem occurs in the Cylinder 2.

I have changed all of the spark plugs, fuel injectors(only cylinder 2 - I just take fuel injector from cylinder 4 and put the second cylinder to check that is the problem is from fuel injector or not), ECU and other electrical components. However, it does not fix.

One of the Mechanical, put the camera to my engine and told that three of the cylinders are oily. He said that, you have to change all of the four fuel injectors. I dont know what I have to do in this problem ...

What are the things that I have to change for that? Maybe the problem can be from the engine ... I really need your help, mercedes bros.

bv9900

Xentry?

TimC300

Which engine do you have, the M271?

So you scanned the car and its showing misfire in cyl #2.

You replaced the spark plugs and you swapped the cyl #2 fuel injector with cyl #4 fuel injector, scanned the car and still getting misfire in cyl #2?

Also there is oil in 3 of the 4 cylinders?

I'm speculating maybe the valve cover is leaking oil.

antboii

Hey @FM099 , did you put new ignition coils when you put in new spark plugs? Also, the spark plugs need to be “clocked” a certain way when you re-install them.

I am with both bv9900 and timc300. Need to get a good scan tool on the car. AND a leaking valve cover is a good suspect for causing mis fires if oil is leaking onto the spark plug. Based on your profile, you have a c250 which is the m271evo engine. There is individual gaskets that go around each spark plug on the valve cover.

I had a misfire when I purchased my c250. Did a full ignition service and no more misfires. Check all your electrical connections going to the ignition coils.

keep us posted!

ant

FM099

the oil is in the 1,2 and third one. not fourth. what i do you speculating also? is it can be from the head gasket?

FM099

yes, xentry

antboii

[QUOTE=FM099;9025780]the oil is in the 1,2 and third one. not fourth. what i do you speculating also? is it can be from the head gasket?[/QUOTE

@FM099 - hey if you are getting oil in 1,2, and 3 spark plugs there is a good chance your valve cover gasket has failed and needs to be replaced. There are individual gaskets that go around each spark plug on the valve cover. Those have likely failed.

Do you have any history of maintenance and oil changes on the car? If not, my suggestion would be to replace the valve cover with a new one. Get a OEM Mercedes valve cover. I purchased mine from the local MB dealership and it came with the gaskets pre installed.

There is a high pressure PCV system and check valve built into the valve cover that can get clogged with sludge and build up if the oil changes were not done Regularly.

there is a video on my YouTube channel showing the inside of the valve cover.

I would also do ignition coils but that is just me !


ant

FM099

I dont really get that, could you please give me an order way of the - which can be possibility of the problem? So , i can start from the cheapest one to the expensive one. I would like to mention it again, it just only doing cold engine - when engine is not cold, there is no misfire - however, power of the engine is significantly reduced.

JettaRed

iTrader: (1)

When you first start the car, is there any smoke from the exhaust? Is the car hard to start?

​As ​​@antboii and @TimC300 have stated, you may have a leaky valve cover gasket that allow oil to infiltrate the cylinders overnight. You should see excess smoke from the exhaust when starting. But I would not think that would cause loss of power once warmed up. Replacing the valve cover gasket is probably the next cheapest test. Another test you could do is a cylinder compression and leak down test. Search YouTube to see how that is done.

jimyj

I’ve seen this issue before, and it can be quite the headache, especially with the W204. From what you've described, it sounds like you might be dealing with a couple of potential culprits. The oily cylinders could indicate a problem with the valve seals or piston rings, allowing oil to seep into the combustion chamber, which can cause misfiring when the engine is cold. Additionally, since you've already replaced the spark plugs and tested the fuel injector, it might be worth checking the ignition coils as they can also lead to misfires, particularly if they are failing under cold conditions.

If the issue persists and you're looking for a comprehensive diagnosis, I highly recommend running a full system scan. The youcanic full system scanner works exceptionally well on these models and can help pinpoint any underlying faults that may not be immediately obvious. Xentry is another solid option, but it does have a steeper learning curve. Hopefully, with a little more troubleshooting, you'll have your C250 running smoothly again—after all, we all know how temperamental these German machines can be!

JettaRed

iTrader: (1)

Hence the question about excess smoke on startup.

In which case I strongly recommend joining @BenzNinja who can provide excellent professional diagnostic services remotely using XENTRY and other engineering software at the software development level.

FM099

Hello, again.

Today, when i launch the car - it turns off , I think it could be same problem as why misfiring. Any suggestions?