Swaglife81

I haven't talked about plugs in a while and mostly in my younger days a few years I always seemed to feel a better response from copper plugs and changed them out every 6-12 months depending. From what I see plugs vary from 3k to 6k in resistance and they are all different. Various NGKs, Bosch doesn't matter. One plug could be 3250k and the other 5500k. Im not a G/Z ecu expert. Most experience was in my Mustang/Chevy days but the ecu in our cars reads resistance in each plug right or at least in each bank averaged out maybe. Kinda curious about lean/rich adjustments with those resistances or if there is a huge gap tolerance that's ecu programmed like... 3500-5500k is normal and so on or if resistance drops below 3000 adjustments are made.

Reason being is tune up time, my tuneups are yearly and I do all fluids, pcv, plugs, thermostat, etc etc and at 35 years of age never lost an engine with 15 years and various drag runs. I don't like just throwing plugs in my car because everyone says oem is best. NGK makes 4-5 versions of plugs and various heat ranges to go with it. Hoping some folks can shine in on some insight without a generic answer like "Use oem it's best"

jhc

You've done your homework. I changed my plugs (diy) @ 90k with generic answer.

rancor

Where did you get that that our cars measure the resistance of the spark plugs?

As for generic answers if you are running a stock or mostly stock engin use stock spark plugs. Heat range should not be changed unless you are adding significant horsepower, nitrous, or boost. The oem iridium spark plugs last forever(100K) as does most of the other parts you are replacing yearly. Are you determined to go back to the 60s or 70s on your car maintenance? The OEM coolant, PCV, thermostat, and stock spark plugs all last a very long time. Coolant depends on what kind you are running. Oem long life is 5 years or 60K mile and that's a little on the conservative side as it assumes you couldn't get all the old stuff out.

EDIT: More research on engine controls.

So according to the FSM the coil packs and spark plug resistance are not taken into account by the ECM. Considering the diagnostics for a misfire where the engine is only looking for a change in RPM again I don't think the ecm has any diagnostic capabilities around the coil packs or plugs. This would mean the engin will not adjust any parameters based on the spark plug resistance.

If the spark plug resistance is enough to change combustion efficiency the change should be picked up by the AFR sensor and the engin will adjust fueling to try and get back to optimal afr ratio. Timing will not be changed based on O2 readings.






So to summarize the Z does not check plug resistance or anything related to the coil packs. Nissan is using the plugs they are because they provide an adequate spark for the stock engine and have an long service life ~100K. By moving to a different makeup of plug you very likely won't change anything performance related on a stock engin and are just reducing the service life of the plug. As for hotter or colder plugs unless you are having fouling issues or detonation issues the stock heat range is optimal for a stock engine.