tiyyara

After looking at various videos on you tube (none of the W204 specific) and checking out what people had said I decided to change my spark plugs today:

Bought original MB spark plugs. Online from MB dealer got all 6 for about 84 USD delivered to home.
You can buy the NGKs or Bosch for 6-9 bucks a piece.
The MSRP on the plugs is 15 USD but I have seen them up to 25 on ebay.
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You will need a T30, Ratchet and a 6 inch extension.
It would be good to have a torque wrench so you can tighten your plugs to specs (more than I would have with a "naked" hand)
15-18 lb-ft

Take our the front cover of the engine, then the air cover with filters after removing both air ducts
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Then proceed with unscrewing the 2 torx bolts that hold the coil onto the plug

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Remove the spark plug: it needs a good effort

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Comparison of the 2 plugs, new and old

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Repeat, times 6

Reinstall the covers

DO not forget to put back the (I think) crankcase breathing pipe.

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You are DONE

skin to skin, about 60 minutes

W204Man

Thanks for the DIY! I just got my spark plugs. I'm going to change them monday. hopefully I will get a little more MPG.

tiyyara

Sorry I was unable to upload all the pictures because of the limitations
If you PM me your email I can send you the rest of the pics

adanmtxt1

What is the recommended interval between changing plugs?

tiyyara

Five years or 91,000 miles

W204Man

I just changed my spark plugs and the rubber things. but now I have a horrible knocking! The only thing i can think of is one of the plugs is not touching the spring. so Im going to take them all out and put them back in. What else could it be? NEED HELP ASAP.
thanks

tiyyara

What are the rubber things? Did you torque appropriately?
What plugs did you use?

W204Man

Im using bosch double platinum 0 242 135 509-000. the rubber thing is part number 2. Everything is torqued right.

tiyyara

Try making sure you "settle" the air filter assembly well
Once when I failed to do that I had the loud knocking noise
Otherwise my thought would be:
Misthreaded plug
Plug lacking "ring"
One cylinder not firing due to mis connection with solenoid

W204Man

I took out all the speak plugs and put them back in. The car is still knocking and sputtering. Im going to put back all the original plugs and see if that fixes the problem.

Heisenberg Merc

It could be that you didnt set your spark plug gap correctly. Im not sure what the gap is for w204 but every internal combustion engine has to be gapped to get proper spark.

W204Man

So i took one new plug out and put a old one in. I found 2 bad spark plugs. Now I have 2 old plugs and 4 new ones. The car will idle for about a minute or so and have a little hiccups in the RPMs. I don't really know what to make of that? I think I'm just going to return the new plugs.

nyca

Where did you buy the plugs? Don't they come pre gapped?

JohnnyC300

Does anyone know a fair price to have this done at a certified mb indy / mb stealership?

I'd like to DIY this but I'm young and have no experience with a torque wrench. Also My car just turned 5 so I guess it's my time. Anyone know of adverse ramifcations of not doing this in a timely manner?

tiyyara

my local MB dealer quote 350 USD

I think 1 year or extra 10k miles should not be an issue.
But risks of going way over in my opinion could be:
1 suboptimal spark, hesitation, cat damage
2 plug getting stuck in head

JohnnyC300

Any visible signs of wear I can look for on the plugs? I am at 50k miles so well under the mileage interval, but manufacture date is about 5 years.

tiyyara

You can check them, but if you remove them to check them you might as well replace them. You will be doing all the work when you examine them anyway

W204Man

I tried gaping the new plugs to the old plugs specs. Now the engine won't start. I give up. I'm putting the old ones back in. I have changed spark plugs on other cars and never had a problem. I just don't know what I'm doing wrong?

calkong

I just changed out my spark plug yesterday. I think you shouldn't have to gap your plug, it should be already pre-gapped but if not, your owner manual should tell you what gap and what spark plug you should get. When you change out your spark plug, put a little bit of anti-seize on the thread.

My car runs more smooth now, I replace the air filter, change out the oil and filter, replace the cabin filter, flushed out my brake fluid and did a transmission fluid and filter change and it feels like a brand new car.

acr2001

With these cars, and the proper plugs, you do not gap them. They already come from the factory with the right gap. The OP mentioned later on that he tried to gap them to match the old plugs. This might be the cause of the issue, if the old plugs were very worn and he tried to match that gap to the new ones (too big of a gap). I doubt it would be sputtering so badly though, so I am at a loss.

Hey OP - no check engine light yet? If you get one you can pull the code and figure out which plug(s) it is.

C300Sport

It's a good idea to check them before install to insure all are at recommended spec. One of the pre gaped plugs I bought for the Audi was way off and needed to be closed in a bit.

LandSeaAir

I noticed on the plugs I pulled out they had brown oil/grease on the threads, Im guessing applied by the factory to prevent the threads from bonding, I'm wondering if i should have put something on the plugs I put in, but don't know what it would be. Then again, if it was on the threads of the plugs I pulled out, Im sure there was more on the threads in the engine.

Bobby204

It's been a few years, have you figured it out? Read somewhere the plug orientation matters? Maybe not? The NGKs seems to have the same orientation by looking at where the thread starts, does that mean they are indexed?

How about coil, need to replace after 110K miles? Dealer quoted $500 just plugs, Pelican has plugs only and plug/coil kit.