M104 spark plug questions
 

95 e320 ..

So I was taking the plugs out and noticed that 3 were Bosch green and 3 were Bosch blue. Resistor and non resistor. I didn’t put those in. About 4 months ago I ad it in the shop for a cel and the mechanic musta swapped things around. Now after thinking about it sorta makes sense with my mismatched wires. I didn’t take note of where each was placed.question how do I figure out what spot needs a resistor plug and what spot doesn’t need one?

https://i.postimg.cc/0bP5nfXq/E7-CE7...2-E7-B27-B.jpg

Specs call for non-resistor plugs on all 6. Bosch F8DC4's match factory specifications and are very inexpensive. The needed resistance is built into the plug boots. There is no exception on this.

A previous owner or mechanic has basically screwed up.

Jayare

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All plugs on that motor should be Bosch F8DC4, no mix and match. Those engines purr with the correct plugs and good wires. If the wires look anything other than excellent, change the plugs, wires and boots on the coils.

Good luck!!!

The wires are karyn brand except for cylinder 1 for some reason. Number 1looks like a old mb wire. So I had it in the shop for a cam sensor cel. They were dragging their feet in working on my car and when they did do work it was just tossing new parts on it without a diagnosis.

So today I took the engine apart to fix the cel. The timing chain wasn’t exactly spot on and I was pretty sure the cam adjuster wasn’t positioned correctly. That’s my bad I did the head gasket job.

Dollars against dimes those plug wires, except for one, are original. Do you have any history on the ignition system? If not, I would budget dollars for all new OE components ie wires, coils and previously mentioned Bosch plugs. You will do yourself no harm. All of the above items are consumable items.

Jayare

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I replaced everything last year when I did the head gasket. Coils are about 3 years old. But I didn’t mix n match everything. Mechanic did that. I’ll order new plugs and wires again. I have 3 w124s I’ll use the extra parts somewhere

i have a 1999 s320. I was using champions,and switched back to ngk. The minisucle amount of spark missed by r plugs is nothing. newer advice say's never use in car's with computers. S Class has one for everything

Jumping on the most recent related thread but maybe someone can point me in the more relevant direction.

Having a grounding issue with my coil pack for 3,4. Grounding stud (spring loaded conductor) holding the coil to the valve cover is really chewed up. My only theory is that a previous/ owner mechanic thought this was a removable screw and used a drill on the soft metal.

The coil will not come off now and its definitely creating rough idle conditions. Anyone out there have any clever strategies for the removable of the coil pack without the complete replacement of the valve cover???

Many thanks in advance MERCI MERCI

Also..

1995 C280, M104 187K

yeah make sure spring cleaned or make a ground wire real easy. I replace coils in sets, or don't believe I took a slow s320 doing 20.5 in the 1/4 mile, to mods to, 14.67 in the 1/4 mile

S320 will run 14s? Stock?

no had to modify engine

PColumbo, try lightly prying under the problem coil pack with a thin piece of wood protecting the valve cover. After you remove the coil pack I would suspect the grounding stud can be removed and replaced. It may be left-hand thread. Best to have MB-trained techs work on your MB vehicles.

As mentioned, Bosch F8DC4 spark plugs (gapped per the Owner's Manual spec) work best in the M104 engines.

My M104.980 has an original label that quotes Bosch, Beru and Champion spark plugs, together with their aftermarket part numbers. So, these are MB recommendations.

I currently have Beru, with an MB star, from the main dealer.

I have used aftermarket Beru, Bosch and NGK. Always the correct part numbers cross-referenced from the MB number. The MB EPC lists 3 MB numbers corresponding to Bosch, Beru and Champion aftermarket numbers.

No difference between them (over the 23 years I've had the car) so don't get too hung up about Bosch.

My last 2 batches of Berus (MB and aftermarket) were made in France.

My engine is the M104.980 but I think the later ones may take the same plugs.

Good hunting.

RayH

Ray, 20 years ago an experienced MB-trained tech advised me to use Bosch F8DC4 spark plugs in the M104 engines. Who would know better than an experienced tech who worked on that vintage MB vehicle regularly?