Dr.Fox

So, I'm at about 72k miles, and I believe it's time to replace the ignition coils.
I was on the highway the other day, put my foot down to make a pass. As the car downshifted to 4th gear and started to pull, I felt a hesitation, then a huge loss of acceleration, and then the CEL popped on. The engine didn't stall or detonate or anything catastrophic, but when I tried to accelerate slowly again it was very sluggish and rough. So as I got off the highway and slowed down, I noticed the car running even rougher without the highway momentum, and it sounded like it was running on <4 cylinders. I turned the car off, and on again, and the engine sounded smooth again.
I immediately drove to my local shop and had them scan the car, and the description was "cylinder 4 interrupt" something or other. The tech cleared the code and told me to drive it until the code came back, to see if the event repeats. Well, it has, and he told me the culprit would be a bad coil.

At this point, although it is on the early side, I think I'll replace the coils, and wires. Any input on this? Should I go with OEM, or OEM replacements? I'd like to do this by myself to save some cash, as I know the labor is easy. I found BERU parts on thepartsbin.com, like $45 a piece. Wires I'm not sure about yet...

SeaCoupe

We don't have spark plug wires. The coil packs plug into a wire harness and then terminate into a spark plug boot.

I have bought and like the BERU brand of coil packs. ( I think that is the brand)

You can change all of them, but really it is hit and miss. Some of the M111 guys have had coil failures that came about quite quickly one cylinder after another. Until all cylinders are replaced My experience is the exception. I have one origional Coil pack that is at 205k miles. IMO, the way to keep a coil pack happy is dielectric grease. This ensures your coil pack doesn't misfire.

To change them out, take off the red cover on the top of the engine. You will see four coil packs. Your 4 cylinder is the closest to the firewall/rear of the engine. Off the top of my head I don't know the size of the torx driver you will need, but it is a very easy job. Given your mileage, i would also change out the spark plugs. DO NOT OVERTORQUE! There is a very good Spark Plug DIY by Splinter.

Let me know if you need specific intell.

Ed

Dr.Fox

Thanks Ed!
So, based on what you're saying, I should only replace the 4th cylinder coil? I think the 100,000 mile service indicates changing the coils at that point, so perhaps I should just buy all 4 now and change them as they go...can't hurt, right? I guess I'm just one of those people who would rather change out everything at once and start fresh!

And, as far as the plugs go, I replaced them about 6-7k ago when I went one step colder for the ASP pulley, so I should be fine there..

The dielectric grease..can I find that at a local auto parts store? And where do I apply this grease?

C230 Sport Coup

I also discovered something interesting lately.
As spark plugs age, they put extra strain on the
coil packs. So, yeh, if you haven't already, change the plugs.

I also was told, that NGK iridiums are good plugs, but you need to change them every 30K or so.
I went 50K and started blowing coil packs like mad.

New plugs seems to have smoothed things out.

Dr.Fox

Interesting...I'm actually running the same plugs as you, sport coup. And yeah, fairly recently.

splinter

Sound advice from emrliquidlife and C230 Sport Coup.
They know the M111 – and of what they post.

C230 Sport Coup

IMHO , yeh, just do all the coil packs at once if you can.
Once one goes, the others will follow suit, and it's a PIA to have them failing
one at a time.
This is one part I keep a spare for in the car.
Sucks driving on 3 cylinders....or ha, 2 even.

I think if you look around you can find a better price, and get free shipping too.
The old pn -
0001501780 Ignition coil (old pn)
is superceded by the new pn-
0001502880- Ignition coil (new pn)
but most places still sell the old pn.

I tried one of the new pn parts, thinking it would last longer, and it failed after 3K miles, but that
was before I changed the plugs, so who knows. They seem identical and most places still carry the old pn. Only place to get the new one is a dealer, and I go with Annapolis MB online. getmercedesparts.com

Yeh, here they are for 35 each, and over 65 bucks is free shipping.

http://www.rmeuropean.com/Part-Numbe..._D4A8868E.aspx

136.48 with shipping.
If you haven't flushed your tranny yet, this is also the only place to get the best price on
MB approved tranny oil, Fuchs brand.

re; dialectric grease.
Use a thin screw driver to run the grease on the electrical contact on the coil pack where it contacts the
spark plugs.
This is easiest done when replacing spark plugs, put in on the spark plug end.

You will find the grease sold at any auto parts store, either in a spark plug change kit, or
by itself.

Dr.Fox

Agreed. I ordered all 4 yesterday. So the dielectric grease should go on the contact between the the coil and the spark plug?

C230 Sport Coup

Yes.

Keep one or 2 of the old packs in the car, the ones that didn't fail, ha but don't them expect them last long.
I also highly recommend putting together a
coupey specific toolkit to keep in the car,
screwdrivers normal and philips various sizes, torx and inverted torx,
metric sockets with the "special" mb sizes like 16mm, metric allens, and a hammer....... just in case.

I found an inexpensive plastic tool box that fit behind the passenger seat perfectly.
Has saved my butt numerous times for small stuff that comes along,
like coil pack changes along the way.
Ha, and having the bottom pans come undone....oh thats a pain.
Got stuck on I5 near Harris Ranch....oh the stench.
Had to pull everything out of the car to get to the jack....
at least I had tools.

I also keep an OBD2 code reader in the glove.
Someone here encountered a code that kills the car till it's cleared!

I also have a CPS in the glove, but no way to be certain it's the right part,
got it from autohaus for like 40 bucks.

Dr.Fox

This is a great idea; I was actually thinking of it today as I was changing the coils out!

So, the car runs perfectly now...however that dreaded CEL is still lit. Will it go off on it's own? Wishful thinking, I know. I should get a code reader to clear it, but I can just go to my mechanic and slip him a few bucks.

C230 Sport Coup

I use this one...
http://www.alpha-bid.com/product69.html