Will YR7MPP33 replace Y7MPP33 with no problem? I just noticed that difference between the old and the new plugs.

No. The "R" designates resistor type spark plug. Only use the spark plug(s) listed in your Owner's Manual for your engine.

__________________
Fred Hoelzle

Is there a negative to putting in resistor plug? Seems most are only stocking the "R" plugs around here..

Yes- it was designed without it.

Don't know the engine by the sparkplug listed. So, it's hard to even guess at possible problems.


Michael

Platt-deutsch, while your motor apparently was designed to run on non-resistor plugs, the jury of your peers (other MB owners) is somewhat divided on the use of resistor plugs. Plenty of M103 and M104 owners report good results with resistor plugs (I'm not one of them), as long as you stay with copper core plugs and stay away from platinum plugs.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

Before he left the forum - MB tech Arthur Dalton recommended NGK non-resistors to replace the Bosch H9DC/H9DCO non-resistor plugs - M103 motor -single cam 6 cyl. He actually felt the NGKs were superior to the "Made in Indonesia" Bosch plugs. I'm speaking figuratively. Indonesia = any 3rd world country that's producing low grade garbage......China/Vietnam/India/etc.

If NRs are what you seek, I would suspect that NGK has an alternative to the now defunct BOSCH NR line.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Seems the resistor is only 5k ohms. At 20,000 volts that wont change things very much at all.. If it was 5 megohms that would probly make a difference. I will run the resistors awile and see what happens. I didnt notice the diff. until I was done changing them. The original plugs were platinum these are identical except they are resistor type. The old plugs looked like new and probly wouldnt have needed replacement at 60K miles but I noticed the gap on the old plugs was about .040 instead of the .031 called for. Is it possible the gap widened that much by itself?

Yep- on my modified Chevy the gap has to be checked every couple of months. Considering everything going on in a combustion chamber it isn't all that surprising I suppose.

As for my 2cents about plugs- I would suggest you try to get as close to what it was designed to run with (which in this case may be a different plug!). And don't bother with any of those $10 octopus plugs- electricity always follows the path of least resistance with all other conditions being equal.

i would go with copper non resistor plugs the ngk are great,platinums dont seem to work well or burn well,plus there not cost effective.

__________________
enjoy life,take the coal that is handed to you and turn it into diamonds. { PHILLIPIANS 4:13}

my mercedes manual mentions champion, bosch, and beru spark plugs. what does happen if you use a resistor plug if something bad were to happen? I need to get plugs too and the h9dc/h9dc0 are now hr9dc/hr9dc0. I know that I can easily call the dealer and they can get the plugs, but I'm tired of being raped in the pockets by them over charging. I try to go by what my manual goes by so I can keep regular maintenance work from becoming unnecessary eff corrections from mistakes or poor judgement.

__________________

1990 190E 3.0L