PeachParts Mercedes-Benz Forum - View Single Post - Non-resistor Spark Plugs

pawoSD · #4 03-16-2009, 11:06 AM

Here is my interesting story:

I got my 300E last November....it was misfiring....so I replaced the distributor/rotor/cap and it got better, then I pulled the plugs....it had nasty old Champion Resistor plugs in it.....I went to the dealer and actually acquired a set of Real-deal Bosch non resistor H9DCO made in Germany plugs. Put them in, it ran amazing....for 60 miles....then it began misfiring bad and was way down in MPGs/power.....so I pull the plugs again, they were horribly coked and dirty. I went to autozone and got a set of super cheap "Splitfire" resistor China plugs.....put them in.....it ran great again for about 100 miles....then back to the same old....but even worse than before....so I put the formerly retired champions back in, but had cleaned them. It ran "ok" from here on....(several hundred miles)....but I still wanted to replace them with good plugs. This time I ordered NGK Resistor plugs online....put them in, and it ran beautifully.....it has been running those plugs for about 2 months....and close to 1500 miles....0 issues. Idles so smooth you can barely tell its running! Plenty of power.....good MPG's....I've been getting 20mpg even when I am a leadfoot.

Moral of the story, get good plugs, and the Resistor ones work fine. NGK are good, and the Bosch Resistor plugs are probably fine too.

The whole resistor/non-resistor thing is a myth.

The only important thing is to not use Platinum plugs as the electrode is too thin.

My 300E does the start/stall thing too....I am guessing it is the injectors or fuel accumulator....but it starts fine after 2-3 seconds of cranking on the second try....so I am not going to worry about it. Once it starts it runs perfectly.