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Discussion Starter #1
My 107 runs rough just after starts when it is humid or raining. Once it warms up there is no miss. Warm starts are quick usually with no miss. So I measured the resistance in the wires, that appear to be original. Wires 1,3,4,5,6,7 each had 1230 to 1280 ohms. Wires 2 an 8 had infinite resistance, I could not measure anything on my meter! The recent NGK BP5EY plugs look okay. So would you replace these wires or let sleeping dogs lie? If so, what brand(s) to avoid or seek. I like OEM but that tends to get pricey.
 

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I had a similar problem with mine except it would run without any problems initially and then after driving for a while it would start to miss. Checked all the plug wires, they seamed ok all measured around 1k Ohm (can’t remember the exact value). Looked at the spark plugs, all looked fine. I finally bought a new set of spark plug wires (mine were still original to the car). Car is running great ever since.
I bought a set of Kingsborne spark plug wires based on some of the recommendations on this forum.
Kingsborne Wire Werks Inc - Spark plug wires, Automotive, RV, Motorcycle, Marine, Racing, Industry
 

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Discussion Starter #5 (Edited)
Agree, sounds like two are shot.
I used Bosch 09028, worked great.
Thanks for that, I would like to use Bosch but Summit says 09028: This does not fit your stock: 1987 MERCEDES BENZ 560SL. Summit carries the same stuff as Rockauto at a higher price. Kingsbourne is giving me a timeout, no results.

Right now I'm considering NGK @ $146 ebay free shipping (can u believe anyone would pay Advance $406 for this same part)?
https://www.rockauto.com/info/100/NGW54245_1__ra_p.jpg
maybe AC Delco ?
https://images-na.ssl-images-amazon.com/images/I/41rCd0NMwZL._SR600,315_PIWhiteStrip,BottomLeft,0,35_PIAmznPrime,BottomLeft,0,-5_SCLZZZZZZZ_.jpg
maybe Standard?
https://i.ebayimg.com/images/g/b3sAAOSwafta1j2e/s-l1600.jpg
 

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I run a Kingsborne set on mine...very pleased with it and would replace with same if the need ever arises.

Kingsborne Wire Werks Inc - Spark plug wires, Automotive, RV, Motorcycle, Marine, Racing, Industry

Edit: Maybe the Kingsborne wire set is no longer an option. Did a search of their site for the part number of the set I ordered back in 2012 (Item# 0000003145)...zero results. Hopefully they just don't stock it anymore but can build a set if ordered. I'd give them a call.
They changed the part number.
08-5666 Kingsborne Spark Plug Wires Ignition Wire Set

The nice thing about the set is that the wires are bundled (for left and right side) just like the original spark plug wires. The individual wires are marked to what cylinder they go on the distributor as well as on the spark plug side. If there is one criticism it is spark plug wire for cylinder #7. If it would be 1” longer it would be perfect.
 

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The performance guys use copper core wires. Do not have to worry about the carbon core breaking down and they deliver more energy to the plugs.
 

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The performance guys use copper core wires. They deliver more energy to the plugs and they do not break down like carbon core wires.
 

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Yes, but Mercedes specification is that the resistance (~1K ohms) is in the wires, not the plugs.
Actually resistance in plug wires and in spark plugs is a throwback to earlier times when the resistance was needed to suppress ignition noise in the the radio. Modern radios do not need that suppression. Also modern spark plug cables do a much better job of keeping the energy inside the cable.
 

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Well, without modeling the electrical properties of the spark circuit from coil to plug, I'm not prepared to tell Mercedes they don't know what they're doing. Tweaking the time constants of the ignition waveform might lead to interesting results.

Me, I'll stick with the manufacturer's recommendations. Even with a 2018-vintage radio in the car (and a 2008-vintage ham radio, too).
 

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Discussion Starter #15
Now that is interesting, the NGK claims to have a copper core conductor as well as ignition noise suppression in their wires. Claim is clipped below.
Yes, but Mercedes specification is that the resistance (~1K ohms) is in the wires, not the plugs.
Actually resistance in plug wires and in spark plugs is a throwback to earlier times when the resistance was needed to suppress ignition noise in the the radio. Modern radios do not need that suppression. Also modern spark plug cables do a much better job of keeping the energy inside the cable.
Well, without modeling the electrical properties of the spark circuit from coil to plug, I'm not prepared to tell Mercedes they don't know what they're doing. Tweaking the time constants of the ignition waveform might lead to interesting results.
Me, I'll stick with the manufacturer's recommendations. Even with a 2018-vintage radio in the car (and a 2008-vintage ham radio, too).
NGK Marketing Description - 2000: NGK wire sets are built to meet stringent OEM tolerances for a variety of vehicles. They utilize a construction method known as variable pitch wire winding to create resistance to radio frequency interference. The variable pitch winding provides suppression throughout a very wide range by scrambling and breaking up the electrical waves radiated by the firing of the spark plugs. NGK wire sets provide superior firing and fuel savings, outstanding durability, excellent noise suppression, and consistent performance.
Core Material: Tinned Copper
Country of Origin (Primary): MX
Emission Code : 1
Insulation Color: Blue
Insulation Material: Silicone
Insulation Outside Diameter: 7.00
Interchange Part Number: Q4 15 0028, 908M, 9909, 09147, 700948, 54245
Life Cycle Status Code: 4
Noise Suppression Type: Yes
Other Part Number: 148004, 671-8131, 127853, 35-8004, 97040, NGK54245
 

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Discussion Starter #16
Installed the NGK wires today. First pic shows why resistance was so high in the Bosch wires, that is corroded green copper dust. Numbers at both ends are recommended. Test drive? Remarkable improvement. I could not detect a miss before but now the car really hums along. I guess I did not know what I was missing.
 

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Those are very good wires. If you have not done so already, you might consider replacing the distributor cap and rotor. They too break down in ways you can not see.
 
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