Now that the action seems to be over, may I toss in an aside? The waste spark system with the two plugs in series is quite common, in my experience. For many years I drove a Ford sedan equipped with a Yamaha built DOHC V6. It used three coils on six plugs, also setup in series. Interestingly, from the factory it was equipped with three each of two different part number platinum plugs. One part number had a platinum center electrode, the other a platinum side electrode. As you would guess, each circuit had one of each. I've also worked on a number of GM cars which used the same design.

- JimY

Very Good..

You may want to clear any codes and might even want to reset the HFM modules memory back to normal base line ..[ that will readapt by itself, but it is easier and better to reset everthing after that type repair b/c the ECU was adapting to the old misfire condition], so you know it is spec now.

The new plugs and connectors are maint. items anyway, so no loss there .. and the OVP is changed to the new part# regardless ..I would stash the old one in the Glovebox/trunk as a spare in case you ever need one on the road b/c a bad OVP on an HFM/SFI can stop the car dead.
You may also want to compare your old coils to the new for Resistance values , with the secondary windings being the ones of most concern.
They will be in K-ohm.

..PS

<>

I see you have another addition aside from the 121 barn find..........
How do you like/dislike the Boxster???
I am thinking about one.

See ya

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A Dalton

<>

That is interesting..so the second plug would have that extra electrode and that would be an improvement on the bosch plug ..
That makes me think my hypoth of why the 104s like the regular coppers over the standard plats has more crediability...that extra electrode on the neg side would possibly aleaviate that firing to the electrode problem of the second in series plug...

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A Dalton

Arthur ... The old and new coil have the same static resistance on both the low voltage side, 0.6 ohm, and the high voltage side, 6.3K ohm. The only visual difference is some swelling around the center bar of the steel core on the sealed end.

The 2001 Boxster 'S' is an OK car but after a couple of years, it still doesn't "fit" me. My thoughts are to "recycle" the Porsche and to try a SLK32. The Porsche is fast, handles like glue, fun on the track but I don't find it comfortable to drive around town, to get into and out of and it is clumsy if you need to carry anything (not much room, even for a cup of coffee). On the other side, friends say that "I look good in it" (it is speed yellow with a hard top). Since it is newer with OBD2, fixing it is easier that this old E320.

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Jim Villers
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"

That's basically what I wanted to know...

Thanks for the info.

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A Dalton

Thanks for this thread guys, it's been very helpful - I've been having the same problems with my '95 E280 M104, now finally sorted with new coils. Arthur, you're a veritable fountain of knowledge on these cars. Thanks for sharing it.

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'96 W124 E280T

This has been an interesting problem. I had posted the initial problem on the MBCA froum and then posted the final solution. There were two people on that board that anre utilizing this information in their trouble shooting.

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Jim Villers
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"

Coil(s) seems to be the common cause of this problem for M104 engines. Had the same problem in my '96 E320 a month ago and it turned out to be a bad coil. Ran perfect one day then started intermittantly missing on the way to work and progressively got worse.

I wonder if it makes sense to just replace the coils once in a while and what that schedule would be. As far as I know, the one that failed on me was original, so that's 245,000+ miles. Surely if they were replaced every 100,000 miles you could avoid having them fail.

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Brian Rogers
'96 E320 traded in at 292,000 miles
'09 C350

A lot of things, particularly the harness problems, are age-related as well as mileage-related, and the youngest of these cars is now 12 years old. Even non-moving parts can degrade over time. But 100,000 miles for the coils seems about right - mine failed at 113,000.

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'96 W124 E280T

My thoughts on these coils [ and connectors] is they are prone to a high fail rate due to extreme engine heat b/c they sit right on top of the engine and then they throw an engine cover over the top. This is definately heat fatique situation and one will notice that these coils are NOT oil cooled..like the old car were..and those old coils , being liquid cooled and remotely located from the engine where they had airflow would last a lifetime..so, not surprizing that a coil that has little cooling AND has to fire 2 plugs in a high compression engine does not have a life time that one would expect from a remote/cooled coil..
One will also notice that the plug connectors that always give the trouble are only the 3 under the coils ..they other 3 are not a as heat trapped b/c they are in the open air and not under a HOT coil..[ that is why we always
point to the 3 connectors under the coils as a first possible on 104 Waste Spark systems

Plus the fact that the originals were weak to begin with [ the blue stickered ones]
This problem can be diagnosed in 5 min with a scope, but for the diyer, persistance and parts swapping, along with some code observations and analytical thinking will get to the bottom of it..

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A Dalton

Arthur .... And a little help from our friends.

My car has 175K miles.

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Jim Villers
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"

Thanks Jim,
I will let the other members know that you get special treatment b/c you have been a Collector Friend for many years and I love the 190SL Group Cap you sent me ..
I was wearing it one day while driving my 250SL and I pulled into a Convenience Store and a guy checking the car out and said "Hey Dude, how come you are driving a 250 and wearing a 190 cap ? " in a smart-ass tone..
I said "Well, I just can't drive both of them at the same time "

" So, do ya' wear a 250 hat when you drive the 190 ? "

" NO , that is when I take the GullWing out ! "

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A Dalton

great thread.

I'm thinking under GP, it's best to replace all coils and their "stubbies" at 150K miles, and keep the rest for spares . . .

:-) neil

I will second that.

After following this thread, I changed the connectors under the coils and my engine misbehavior disappeared! Now I actually notice the poor shocks in the front of the car and the non functional AC. Before I was too busy hiding behind the wheel trying to drive the backfiring beast back and forth to the airport each week.

Surprisingly, my car just hit 149,000 miles to boot. Perhaps the interval for the stubbies should be 125K.

Great Thread and thanks for the bump - I thought I lost this in the sea of posts. I now have bookmarked for further notes and evaluation.

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Brian G.

1994 E320 Wagon with many warts SOLD
1995 E320 Wagon with a beauty mark or two FOR SALE

Most interesting post! I just changed the coils of my 1996 E320 at 135K preventively. With "stubbies" do you mean the connectors, wires or plugs?

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1996 E320 since 1/16/08, 171K miles as of Feb 2011

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1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE