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Non-Resistor Spark Plugs: What a difference!

11K views 13 replies 6 participants last post by  jzchen 
#1 ·
So I'm sure most of you are aware that our cars are designed to use non-resistor copper spark plugs. For the last 7 years I had been running the Bosch HR9DC0 which are resistor plugs. (mainly because AutohausAZ had them for $1.50)
My car has it's upcoming biennial emissions test and I always like to change plugs and oil before the test. This time I decided to order a set of NGK BP5EFS from the UK. These are slightly hotter plugs than stock, I'm using them to help keep emissions down as the M103 puts out more emissions when cold.

I paid $2.93 per plug plus around $6-7 for shipping. For some reason NGK US won't list the non resistor plugs on their site.

I tell you what a difference the non resistor plugs make! Before I had a bit of hesistation when accelerating and the engine didn't have the smooth power that the M103 is known for. With the new non resistor plugs acceleration has smoothed out, throttle response has improved and the motor pulls hard when kickdown is engaged. So do your W201 a favor and install some non resistor plugs if you haven't already done so!
 
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#5 ·
No, I'm afraid they are resistor plugs.

But the manufacturers do not make the non-resistor types with the the fancy metals that keep your gap nice and consistent. I am no longer active in the W126 side because a moderator decided to dig up an old post about some expensive paste/lubricant I got for my W123 sunroof, partly because I was having a hard time with water leaking into the passenger rear foot well.

Anyways, another moderator noted issues with relays failing. I have no experience with fuel pump relays failing. Could be EMF/RFI from the non-resistor plugs. Exactly the reason Bosch decided to put resistors in plugs, to protect sensitive electronics....

I have been using them. They work great. If an issue comes up while using them, I'd immediately look somewhere else than go after the plugs....

If I had been on this forum before I had made the switch, I'd be afraid too after reading here, but I switched way before coming to benzworld.
 
#7 ·
So do your W201 a favor and install some non resistor plugs if you haven't already done so!
umm... this beauty has been running happily on Bosch Iridium plugs for almost 2 years now. would not go back to any other type of plugs that would require cleaning and regapping... ; )

Its saving me about 20-30 gal per week, starts on first crank with push button, and snaps on a push of gas pedal : )
 

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