Misfires, Dielectric Grease, Coil Packs and Spark Plugs
Thread Starter
MBWorld Fanatic!
Joined: Jun 2002
Posts: 7,263
Likes: 169
From: So. Oregon Coast
C230 Sport Coup + 2006 W164 ML350 + 99 Ford Escort RIP
Misfires, Dielectric Grease, Coil Packs and Spark Plugs
My experience with the M111 engine is that about every 50K miles the
Coil Packs fail.
This has been fairly consistant. However another member had told me he
hadn't had any issues with CP's with over 100K miles on them.
But unlike me, he had been using dielectric grease on the connections.
So recently when one of the CP's thats already been replaced, began to appear to fail I applied the grease.
The CEL is tripped by a mathematical formula of X number of misfires out of
X number of fires. I couldn't get it to do it again, but could feel the misfires.
If it's less, it may not trip the CEL. This can still cause issues with other parts of the car like the Catalytic Converter.
Anyway, so this time instead of just replacing it (yup, right around 50K miles on it, like clockwork) I thought, hey maybe I just need to put dielectric grease on it, since I hadn't been doing so in the past.
Amazingly the misfire went away. Today, I did the other 3 CP's putting a little of the grease on the end of a small screwdriver and putting it on the end of the plug, and also on the conductive end of the CP.
The car is running much more smoothly, whereas before I was getting a small amount of shaking.
Just an FYI- When you change your spark plugs, or replace a coil pack
be sure to use dielectric grease.
I can only assume that heat, along with humidity over time (I leave near the coast) causes some corrosion.
I'll keep everyone posted and see if this extends the life of the coil pack.
Coil Packs fail.
This has been fairly consistant. However another member had told me he
hadn't had any issues with CP's with over 100K miles on them.
But unlike me, he had been using dielectric grease on the connections.
So recently when one of the CP's thats already been replaced, began to appear to fail I applied the grease.
The CEL is tripped by a mathematical formula of X number of misfires out of
X number of fires. I couldn't get it to do it again, but could feel the misfires.
If it's less, it may not trip the CEL. This can still cause issues with other parts of the car like the Catalytic Converter.
Anyway, so this time instead of just replacing it (yup, right around 50K miles on it, like clockwork) I thought, hey maybe I just need to put dielectric grease on it, since I hadn't been doing so in the past.
Amazingly the misfire went away. Today, I did the other 3 CP's putting a little of the grease on the end of a small screwdriver and putting it on the end of the plug, and also on the conductive end of the CP.
The car is running much more smoothly, whereas before I was getting a small amount of shaking.
Just an FYI- When you change your spark plugs, or replace a coil pack
be sure to use dielectric grease.
I can only assume that heat, along with humidity over time (I leave near the coast) causes some corrosion.
I'll keep everyone posted and see if this extends the life of the coil pack.
Last edited by C230 Sport Coup; Jan 30, 2009 at 06:20 PM.
Senior Member
Joined: Aug 2008
Posts: 273
Likes: 6
From: SE PA
2001 C320
I doubt it, but do you know if the M112 engine uses the same coil pack as the M111? Also, do you have any diagrams of where exactly on the coil pack you put the dielectric grease? This sounds like something very easy to do and should be done regardless if someone is having problems or not.
Super Moderator
Joined: Jun 2008
Posts: 19,942
Likes: 192
From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Tru - as with PS pumps - I know of 2 X 240s - one at 700,000 Km & one at 550,000 Km never had coilpacks & still running perfectly. In fairness both have run their mileage fairly quickly.
Trending Topics
Super Member
Joined: Aug 2007
Posts: 876
Likes: 81
From: Phoenix AZ & Cayucos CA
’27 AMG SL55(ordered), ‘23 EQS 580 SUV, ‘19 AMG E53 Cpe, ‘48 Willys Jeepster
It's not just MBs, the wife's Audi TT 3.2 fried a coil pack a month ago. I wouldn't have minded it just mis-firing, but the bit about it catching fire and frying the connector in the middle of nowhere in the snow was a bit annoying. And if you think MB service is bad, it took Audi a week to get and replace a $20 usd connector.
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
MBWorld Fanatic!
Joined: Jan 2006
Posts: 3,212
Likes: 8
From: Pasadena, CA
2002 C230K, 2013 BMW 328, 2015 BMW X5
Super Moderator
Joined: Jul 2006
Posts: 3,365
Likes: 12
From: Orange County, CA
GMC - Miata - Trek - P-Car
In my current issue of Underhood Service, there’s an interesting – albeit generic – article regarding coil-on-plug misfires.
www.underhoodservice.com
www.underhoodservice.com
Thread Starter
MBWorld Fanatic!
Joined: Jun 2002
Posts: 7,263
Likes: 169
From: So. Oregon Coast
C230 Sport Coup + 2006 W164 ML350 + 99 Ford Escort RIP
I've come to the conclusion that the little spring that contacts the plug becomes corroded.
Though, I had 4 fail that were either factor installed or from the dealer, but don't beleive they used the grease.
I did recently end up replacing the #4...again.
Which likely means the other 2 replaced at the same time are next.
Though, I had 4 fail that were either factor installed or from the dealer, but don't beleive they used the grease.
I did recently end up replacing the #4...again.
Which likely means the other 2 replaced at the same time are next.
Super Moderator
Joined: Jun 2008
Posts: 19,942
Likes: 192
From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
In my current issue of Underhood Service, there’s an interesting – albeit generic – article regarding coil-on-plug misfires.
www.underhoodservice.com
www.underhoodservice.com
Thread Starter
MBWorld Fanatic!
Joined: Jun 2002
Posts: 7,263
Likes: 169
From: So. Oregon Coast
C230 Sport Coup + 2006 W164 ML350 + 99 Ford Escort RIP
MBWorld Fanatic!
Joined: Jan 2006
Posts: 3,212
Likes: 8
From: Pasadena, CA
2002 C230K, 2013 BMW 328, 2015 BMW X5
In my current issue of Underhood Service, there’s an interesting – albeit generic – article regarding coil-on-plug misfires.
www.underhoodservice.com
www.underhoodservice.com
T, I don't know if the spring is the issue. When I have gone through my CPs, I have found my springs to look like miserable little pieces of frail twisted wire. But they still work.
E
Senior Member
Joined: Aug 2008
Posts: 273
Likes: 6
From: SE PA
2001 C320
I doubt it, but do you know if the M112 engine uses the same coil pack as the M111? Also, do you have any diagrams of where exactly on the coil pack you put the dielectric grease? This sounds like something very easy to do and should be done regardless if someone is having problems or not.
MBWorld Fanatic!
Joined: Nov 2001
Posts: 5,851
Likes: 196
From: Huntington Beach, Ca.
'17 Jaguar XF
I waited for the 100K mile interval to replace my plugs. They looked great when I removed them and probably could have gone another 100K miles. Still had the proper gaping. These modern motor management systems and lead free gasoline really improve plug life.
Senior Member
Joined: Aug 2008
Posts: 273
Likes: 6
From: SE PA
2001 C320
Hmmm, if that's the case, I may just do that. In the meantime, I may take out a few random plugs from each cylinder bank to check on their condition. I'm assuming they are platinum plugs? On the newer GM vehicles, (like my 1996 Blazer, they have the 100,000 mile tune up) where at 100,000 miles, is when you actually change the plugs, wires, rotor and distributor cap.
Super Moderator
Joined: Jun 2008
Posts: 19,942
Likes: 192
From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
I'm well aware of that. I think splinter was posting in the broader sense of individual coil pack per cylinder & if you understood the article - the reason for coil overheating - OTHER than ambient heat.
Super Moderator
Joined: Jun 2008
Posts: 19,942
Likes: 192
From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Super Moderator
Joined: Jun 2008
Posts: 19,942
Likes: 192
From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
After reading through this thread to this point, I guess other people’s replies answered my own question here. So the M111 uses 1 spark plug per cylinder, while the M112 (and I also believe the M113) use two plugs per cylinder, interesting. I have just recently reached 70,000 miles on my C320 and was planning to change out the plugs. More than likely the OEM Bosch's. However, after reading this thread, I think I'm going to use the dielectric grease on the spark plug connector.
Last edited by Glyn M Ruck; Feb 27, 2009 at 03:59 PM.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2002
Posts: 7,263
Likes: 169
From: So. Oregon Coast
C230 Sport Coup + 2006 W164 ML350 + 99 Ford Escort RIP
I figure 60K miles between spark plug changes.
Others around here have had the opposite experience.
Waited till close to 100K mile and the plugs were toast.
Others around here have had the opposite experience.
Waited till close to 100K mile and the plugs were toast.
Super Moderator
Joined: Jun 2008
Posts: 19,942
Likes: 192
From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
MBWorld Fanatic!
Joined: Nov 2001
Posts: 5,851
Likes: 196
From: Huntington Beach, Ca.
'17 Jaguar XF
Probably on the S/C 4 bangers. I was so impressed with the condition of the plugs after 100k miles that I kept a few just to show people.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2002
Posts: 7,263
Likes: 169
From: So. Oregon Coast
C230 Sport Coup + 2006 W164 ML350 + 99 Ford Escort RIP
Wow, that is impressive. I once had a defective set of Bosch plats.
They were shorting through the insulator starting around 500 miles...causing misfires.
And finally it just stalled out at about 1000 miles in the pitch dark.
I opened the hood and could the arcs. Replaced plugs, and problem was gone.
Never used Bosch Plugs again.
They were shorting through the insulator starting around 500 miles...causing misfires.
And finally it just stalled out at about 1000 miles in the pitch dark.
I opened the hood and could the arcs. Replaced plugs, and problem was gone.
Never used Bosch Plugs again.
