I have a W210 '97 E420 that codes up a #3 cylinder misfire. My indie tells me after diagnosing that I should be replacing all of the coils and plugs and connectors. Car has 146K and just had a major tune-up at 117K.

Shouldn't this have been done at that time? Should I be replacing all of the coils along with supposed new plugs that have already been replaced?

Any words of wisdom??

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Norm K.
'97 E420 Sport
'06 E350 Sedan
'67 Mustang Coupe
'70 F-250
'15 VW Jetta

http://catalog.peachparts.com/ShopByVehicle.epc?q=1997-Mercedes--Benz-E4--0-Engine--Electrical&yearid=1997%40%401997&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6398%3AMBC%7C1578%3AED%7C10000074%40%40E420&catid=240798%40%40Engine+Electrical&subcatid=240801@@Spark+Plug+Connector&mode=PA

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A Dalton

buy the coil sticks and cross your fingers. i've had to put coils on cars when the plugs weren't changed until a light came on. that's why i like to change plugs every 60k. it's easier on the rest of the system. good luck, chuck.

Your indie is wrong.

You should replace all the plugs and the connectors because they tend to go bad when plugs are replace at your age and miles.

If you still have the miss after the plugs and connectors, then simply swap a coils with another cylinder. If the problem moves, you found the bad coil.

No need to use a shotgun approach and replace all the coils right of the bat. Good $$$ for your mechanic, but bad for your wallet.

If I had to guess you just need the plugs and connectors, and perhaps one coil.

I would make darn sure the coil was bad before I replaced it.

Most often the connectors go bad, I would replace the plugs because you know one is going to be fouled and they give you a new baseline to follow.

Do it soon, you don't want to melt the cat.

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Obama has to be popular and has to accommodate himself to the comprehension of the least intelligent of those whom he seeks to reach.

Thank you all for the comments and advice. This seems to be a DIY and am going to do that on Monday when I can get the parts. Not driving the car till then.

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Norm K.
'97 E420 Sport
'06 E350 Sedan
'67 Mustang Coupe
'70 F-250
'15 VW Jetta

As JC states, it is the connectors that are No 1 on the mis-fire list. That is the part I posted.
The reason they go bad is b.c they are not just a connector, they have a Resistor inside and that is what deteriorates from heat and use.
Most Techs know of this common fault and will auto change the connectors when changing plugs.
If you want a quicky test, change that one , clean that plug , and retry the car.
Correct diagnosis is a scope test, but a swap works for the DIYer.

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A Dalton