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Non Resistor Spark Plugs and "Coil on plug" Ignition

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Can I have peoples thoughts on this please, are "non resistor" plugs damaging to the coils or ECU?, i'm sure I have read somewhere that you must use a resistor plug.

i will start with what personally happened with me: the bad events

(1) Haltech E500, car starts.. makes a pull, cuts off (no reason)..., start again log into ecu... cant get in... kills motor, ign on login in, starts motor, revs, then goes dead... looks at the ground wires, power wires, all good, 15 mins of trying a number of things, "we need to change the plugs in any case do it now." NGK racing non resistor" plugs came out, NGK resistor type went in. no issues...

(2)Maxxecu Race ecu 2JZ, Random trigger errors, pulled the plugs same "NGK racing non resistor" dropped in new set on of "NGK racing non resistor" same thing, drop in NGK Resistor plugs" no errors (note this happens on 2 different cars.)

(3) Hondata s300 , random (laptop would not connect)... change to resistor plugs ... no issues

Now from other sites:



now i must say, i have had cars that ran resistor plugs with no issues. i still now, never buy non-resistor plugs.

damaging to the coils or ECU

that i have not seen.

Hi Kester,

Thank you very much for the reply, Yes, I have had odd issues with non resistor plugs in the past, I think the cause may be "Radio frequency" related interference.

Again, thanks for the reply.

no worries, sometimes i feels as if it just me having these issues as i have not heard any one really talk about it. What i don't get is why some cars and not others.

I've heard similar reports of comms problems and cam/crank noise that are solved by swapping from non-resistor to resistor spark plugs.

I haven't heard of coils or ECU coil drivers getting damaged from the use of non-resistor plugs.

When the spark jumps the spark plug gap, that generates some magnetic interference. Non-resistor plugs usually result in a stronger spark which will generate more magnetic interference. I say magnetic interference rather than radio frequency but the interference/noise does travel through the air. If you happen to have an oscilloscope, the probes act like an antenna and pick up this interference (even when using resistor-type spark plugs) when measuring a signal that you know is stable like a 5V sensor reference supply.

I don't know if it's actually helpful to have a stronger spark than what's needed to light the mixture, for instance I've never seen or heard about dyno data showing more power due to switching from resistor- to non-resistor plugs when the engine was already running clean (no spark blowout) on the resistor plugs.

Thanks for the reply Scott

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