Pete's opinion
 

Benz designed resistance into the wiring/terminals. The use of resistor plugs upsets the ignition equation and will result in suboptimal efficiency.

My solution, eliminate spark plugs altogether.

Denso's T20EP-U's are pretty easy to obtain. They cost $2/each last time I bought some. I bought 12 last time around so I'd have some for the next change. I wouldn't go through all that extra stuff.

I run denso 5061 spark plugs,there are like the 3 groundstrap plugs bosch makes,that came with my car

These are also resistor plugs. Your car has a different ignition system than the OP's 190E 2.6, it might not suffer the same ill effects.

How are you going to light the fuel? With a match?

Someone said that it's best to rely on your MB dealer selling you the right plugs. NO!

My MB dealer sold me 2 lots of resistor plugs for a total of 200 Euro before I took the matter in hand and put in non-resistor Bosch plugs. Result: more even idling and eliminated misfire. This on a 1991 M104.980 engine.

I now get Beru or NGK for about 2 Euro each and all is well. MB in my neck of the woods (France) can be utterly clueless on older car issues.

It is most important that all HT components on my engine (and similar) are of the highest quality and in perfect condition. For me, this means MB for everything apart from plugs. Failing that, Beru or Bosch caps and rotors. NOTHING else, in my opinion.

The best to all.

RayH

You can always find the NR plugs @ the dealer...if you joing MBCA you get wholesale pricing. No fuss/no muss!

Or, order a bunch off of parts.com and request a shipping quote to keep it reasonable!

Jonathan

What is all this $4-5 plug bull**** I keep hearing? You can get Bosch non-resistor plugs on the web for under $2. I paid $1.50 each from the Auto parts Haus that's in AZ.

If you Read fully you'll note that I say Worst case scenario you can source the Correct/Proper plug from the dealer for said 4-5$

Not all NR bosch plugs are available on the aftermarket stateside.

Then you either got lucky, ordered the plugs several years ago, or you did not read the label correctly. That website in AZ offers resistor type plugs. Also, keep in mind I'm referring to the Bosch H9DC/H9DC0 for the m103 engine. If you go back go back to the website you will see that they offer H"R"9DC plugs.

Reading this thread jogged my memory of this great post by mercmad6.3:

"He might not have,but I have had plenty of experience dealing with older Mercedes wrongly fitted with carbon string leads and resistor plugs. Mercedes Do not need suppressor leads as from 1937 on wards you could buy suppressed or non suppressed distributor and plug terminals for this very purpose. From the mid 1950's nearly all gas Mercedes came equipped with the suppressor plug terminals (5kohms) . From the 1970's all came with a resistor in the rotor (always check old rotors )
and then the distributor terminals as standard. Right up until the 1990's all Mercedes still had solid core leads,and for a very good reason. it is reliable and it is the best. The resistor plug terminals slow the spark down from a bright instant flash to a slow(relatively) arc almost. This Promotes better combustion . Use a carbon string lead ,which are nearly always offering too much resistance and you are asking for unreliability ,mostly hard starts and all that it leads too."

Here's then whole thread:

http://www.peachparts.com/shopforum/vintage-mercedes/349465-pertronix-radio-interference-mystery-solved.html

Years back when it was made known that the Bosch NR plugs were going off market, I bought several sets. I'm covered.

Similar situation occurred with R-12. Did you load up before it was no longer available without license and gouge pricing?

Ok, well I did it. I converted resistor plugs into non-resistors. when I explained it it seems like a lot, but the reality its that it takes only about 5-10 mins for all the plugs and you're done. Unscrew the tip, take out resistor, put in a core, screw the cap back on.
http://www.peachparts.com/shopforum/tech-help/350345-resistor-spark-plug-converted-into-non-resistor-spark-plug-pictures.html

Just wanted to let you know that I borrowed one of your pics in this post:

http://www.peachparts.com/shopforum/3277215-post9.html

My post suggests that there is no need for non-resistor plugs if using the current Bosch or in fact almost all aftermarket wire sets on our old cars.

I read today at NGK website that resistor plugs,are better for computer controlled cars.It says the noise(dirty voltage) from non resistors are damaging to the computers.

Looking through plug part numbers at Advance for my '88 420 it has a Bosch P/N 7905 listed. It's a Bosch Super Plus Copper Core plug. My question is... is this a non-resistor or resistor plug. The new P/N W8DC would be for the non-resistor. If there's a R ,as in WR, in the Bosch p/n would mean resistor correct?