NGK Iridiums
 

Hi, I just changed my 92 500SL's plugs from the Bosch ones to NGK Iridiums. It ran sweet as a nut for the test run of 20 miles. After that it sat for a couple of days untill tonight when I took it to the supermarket and it started to miss quite bad once normal running temp was reached.

After searching here I've found that the replacement plugs may have been the wrong choice. I have always run them and found them to be good.

The car has just over 60k miles on it and has been a mint runner since I've owned it.

Whats the difference between a resistor plug and a non resistor plug? And how does this affect the Merc engine?

Cheerz in advance, Tim, N.Z.

That type of plug "shouldn't" have any adverse affect on the way that engine runs!
The very little extra resistance is barly measurable.

I would take a good look at the distributor caps & rotors.

Yeah, the new plugs could have pushed an already worn out cap/rotor over the edge. Not that it's the plugs fault, just the fact that there is a decent plug there where before there wasn't. Can't say I've seen this on an MB, but I've seen it on many other cars...... I don't have much experience with MBs.....

iridium plugs are fairly new and what the newer cars are running and run very hot since the newer engines need to run hot to be the most efficent.

I did change back to the Bosch plugs today and it is running fine again. Although the difference in colouration between the two types was interesting. The Bosch plugs when I removed them first time were a beautifull tan brown and the Iridiums had a white powdery, dusting on the very ends.

Maybe I should check the dizzy cap and leads. But with only 60,000 easy miles would this be premature for a worn cap and leads?

Nevertheless, I will check into it as the performance and crispness of the engine with the Iridiums is worth the effort for sure.

To be updated...

Cheerz for the help.

I don't like NGK plugs in Mercedes motors. I have heard many story of how they caused the motor run very poorly. Your ignition system was designed on Bosch parts and thats the way it needs to be.

Spark plugs are spark plugs, NGK make high quality units. My 300E has been running Resistor NGK plugs for thousands of miles and it runs great. I used the dealer non-resistor bosch plugs in it, and it drove 58 miles before they coked up and started misfiring.

I've heard countless stories about how Resistor plugs won't work in a M103, and yet I've been running them for a long time with 0 issues aside from excellent power, smooooth idle, and good mpg's....

And isn't "iridium" a cool name?

I run NGK BP6EFS in my M103-12V twin turbo coupe.

After two years and about 6K miles the car dyno'd at 302 torque at the rear wheels on a Mustang load dyno...
That's about 390 torque at the crank..
Doubtful Bosch plugs would have given any more power....

I want a twin turbo M103!!! :eek: That'd be sweeeet.

Maybe a cool name but they are many times the price of a plain ordinary set of non resistive NGK BP6EFS's.

As already mentioned modern engines run far hotter than the "legacy" models.

[QUOTE=Ivanerrol;2182858]Maybe a cool name but they are many times the price of a plain ordinary set of non resistive NGK BP6EFS's.

I got mine through Ebay. Paid about $14 New Zealand dollars each landed at my doorstep. Way cheaper than $27 NZD each we pay here. Platinums are even more expensive!

Any ideas on the white powdery stuff?

[QUOTE=Benzyne;2183021]The equivalent of NZ$14.00 buys me a whole set of six NGK BP6EFS's.for my M103, here in Oz. ;)