Hi guys!

I changed my spark plugs this weekend after getting 2 missfires in one month and I thought about making a DIY. Changing your spark plugs is an easy job but it's easier if you already know what spark plugs you will need and what sockets,etc.

You need a E8 socket with a narrow head for the coil packs. Make sure you get one that is one pinky long and quite thin. You will need to get inbetween the coil pack connectors. A 16mm spark plug socket, a long extension for the spark plugs. And of course ratchets to fit them on. Also some tape to tape up the 16mm socket to the extension and a flat head screwdriver will come in handy. I need to use the tape because the 16 mm socket is pretty tight around the spark plug and otherwise I keep pulling the extension out the socket to pull the spark plug out of the engine.



For the spark plugs I used PLKR7B8E by NGK. It was the number on the spark plugs I pulled out of the engine. Except that I got the NGK brand ones not the NGK's Mercedes marked spark plugs that they fit with the same number from the stealership.

You can also use:
Bosch 0 242 140 512
Denso VXUH22
NGK PLKR7B8E
OEM 0041594403
OEM 0041595803



1) Remove the engine cover. Just give it a pull on the sides. It comes off easily




2) On the center of the engine there are for coils conected to 4 connectors. Locate the 4 connectors and pull them out. The flat head screwdriver might help pulling them out.




3) Use your E8 socket to remover the 2 bolts holding each coil on the top and bottom.




4) Pull out the coils. They are jammed in there so give them some elbow grease. The 3th coil needs to be turned a bit to clear a sensor. You can also remove the sensor but it isn't necessary




5) Take your extension with the 16mm spark plug socket on it and slide it down the hole to put it on the spark plug and unscrew it.



6) Pull the old spark plug out and insert your spark plug into your socket. Slide it back down and screw it back in. Check your package about the tightening of the spark plugs. The NGK's I used needed to be tightened one half twist.

7) Put back the coil packs and screw them back in.

8) Plug every coil back in and check evertyhing.

9) Put the engine cover back on.

10) Done!

 

Very useful! Thanks much!

 

You're welcome!

 

I also had spark plug misfire on my C250 at 22,000 miles. The dealer changed out 2 plugs. I now have 2 NGK and 2 bosch. #1 & #2 were flagged as misfiring. Just prior to the misfire i was also noticing hesitation at starts and shifts. Then plenty of soot coming from the tail pipe. Since then my mileage dropped to 26.5 mpg highway. M-B says nothing wrong, but my own investigation found using BG products upper valve- injector cleaner reversed poor gas mileage for a temporary time. Only to return about 5000 miles later. There must be something running way to rich to foul plugs, cause soot out of the tail pipe and load the upper cylinders to where they need cleaning. Especially at this amount of low mileage. Am i a fluke or does the EPA need to take a look at whats coming out of my tail pipe. M-B dealership changed tail pipe tip to reduce carbon buildup on my white bumper.. talk about solving the problem?!?! And i'm from Detroit. They must think i'm stupid. So anyone else with a C250, misfires, poor gas mileage and sooty tail pipes???

 

Do you have any mods installed? I used to have bms intake and tune installed and noticed gasoline odor coming out of tailpipe. After uninstalling the odor is not as strong. Mods could be messing with air/fuel mix.

 

Only "Mod" I have is replaced th estock air filter with a K&N. same price.

I have even cleaned the K&N to see if that would change the MPG and it did not. I've been using K&N filters in cars and trucks for over 12 years without issue.

One thing I did find in a cross country trip- gas with ethenol definately lowers gas mileage. Gas east of the mississippi is better gas mileage than western gas. I can rarely find a station that is 100% gas and if it i sit is 89 octane.

I may have to resort to my NORTON days of filling up with aviation gas.

A buddy with a kid in Air Force in Germany says Germans would NEVER put ethenol blend in their cars...

MB put a new tail pipe extender on my car to eliminate soot on my white bumper.. the tail pipe is loaded with black soot. Why am I seeing soot??
They take your money --you take your chances.

 

I'd say take it to another dealer.

 

A quick question... What is the proper plug gap?
Thanks.

 

Thanks 190Benz for the great tutorial!!
Replaced them today with improved engine performance results. I'll have to wait and see if my mileage improves.

 

A pic of both old & new... (Also shown in another thread for total inappropriate redundancy)