[Travis Rickert]

Hello -

I have a 2006 C230 Sport with 73,339 miles that has a check engine code of P0301. When checking the code out and doing a leak down test, the cylinder came back with 50% leak down (carbon build up or bad valve causing the problem).

How do I fix this? Can this be fixed relatively easy without going to an MB mechanic?

 

[tjts1]

Can this be fixed relatively easy without going to an MB mechanic?

No.

 

[Saints&Sailors]

Hello -

I have a 2006 C230 Sport with 73,339 miles that has a check engine code of P0301. When checking the code out and doing a leak down test, the cylinder came back with 50% leak down (carbon build up or bad valve causing the problem).

How do I fix this? Can this be fixed relatively easy without going to an MB mechanic?

P0301 is a misfire code for cylinder 1. Given that you already did a leak down test I assume you are fairly familiar with engines. Generally, misfires are the result of improper spark, fuel, or air ratios. Simple stuff first (you probably have already done a lot of these):
-- Did you check the spark plugs? Might be a good time to change them with the correct spec'd parts.
-- Ignition coils might be bad - not sure if there is a procedure out there to test them? I'll let someone more knowledgeable chime in.
-- Did you perform a compression test as well? Might be good to find out these numbers.
-- While it could be carbon build up, at 73k miles you shouldn't have too much of this. Cleaning out the combustion chambers might be a good exercise though.
-- Check the pressure coming in on the fuel line. I don't know the specs but you should be able to look them up to see if the fuel pressure is a little low which may cause cylinder 1 to misfire - it should be the cylinder farthest from the fuel pump.
-- Might be a good time to clean out the throttle body too.

Misfires are a pain - you'll feel like you're just chasing things and throwing parts at it. Look at the bright side though - once you're done, it'll be like you have a new car!

 

[Travis Rickert]

Thank you for your response.
I have replaced:
-spark plugs (they needed it)
-ignition coils
-camshaft sensors

I found out that the prior owner of the car only used regular unleaded gasoline the entire time he owned the car.
I pulled out the #1 spark plug and used an endoscope to look inside cylinder #1, and I see that it has a large amount of carbon built up all over. So, it looks like I need to tackle the carbon build up.

Next step is to figure out the best way to get ride/remove the carbon build up that is easy enough for me.

 

[Saints&Sailors]

Thank you for your response.
I have replaced:
-spark plugs (they needed it)
-ignition coils
-camshaft sensors

I found out that the prior owner of the car only used regular unleaded gasoline the entire time he owned the car.
I pulled out the #1 spark plug and used an endoscope to look inside cylinder #1, and I see that it has a large amount of carbon built up all over. So, it looks like I need to tackle the carbon build up.

Next step is to figure out the best way to get ride/remove the carbon build up that is easy enough for me.

They only used regular unleaded gas in it? Ouch. That was definitely penny-wise and pound-foolish on their part. Saved them a few bucks at the pump only to have the engine full of carbon after less than 80k miles. Sounds like you we're on the right track all along. How do you plan to clean out the carbon build-up?

Most of my prior automotive experience is with Jeeps (my 2000 TJ has an intermittent P0301 misfire code a couple years ago) so I've used Seafoam and combustion chamber cleaners but I'm always hesitant to do so with a Merc since they are quite a bit more sophisticated than the old inline 6 cylinder/4.0L engines that Jeep uses. If you're willing to try it, Seafoam has a spray version that you should be able to use on your C230 (the regular kind you won't be able to get directly into the cylinder since I don't think there is a vacuum-assisted brake booster line on the w203 - perhaps C230s are different?). Mopar had a combustion chamber cleaner that they sold which was similar. I would think Mercedes would have a similar product but, again, I defer to others on this forum who are more knowledgeable.

Out of curiosity, did you check the throttle body? While you're at it, it might be a good exercise to clean that out too.

 

[Noorzad]

Hello -

I have a 2006 C230 Sport with 73,339 miles that has a check engine code of P0301. When checking the code out and doing a leak down test, the cylinder came back with 50% leak down (carbon build up or bad valve causing the problem).
if
How do I fix this? Can this be fixed relatively easy without going to an MB mechanic?
there is an old trick we used to use to remove carbon built ups, use at at your own risk (Risk= if there are hard hard carbon it might mechanically damage the engine) get a small water bottle and put water and connect a long vacuum hose manifold, run the engine between 2000 to 2500 RPM while engine running dip the loose end of the hose in and out of the water bottle to suck water. don't keep it in for too long otherwise engine might die..... repeat this a couple of times.....if you have lots of carbon built, you will see gray smoke come out....otherwise white puff of smoke...
at the end reset OBD II codes if any.....

 

[rudeney]

Welcome to the forum @Noorzad - please take a moment to read the information on the link below. It explains how to update your user profile so that your car's details and your location appear on each post below your avatar. This is good information for others to know when trying to help. It also has good information about how the forums are organized and how to use the search feature:

Find your Forum Section, Navigate & Search

I would not use the water method - it's too easy to ruin the engine that way. If you truly think it's carbon buildup, I'd dump a bottle of Techron into the tank and drive it like I stole it.