Ignition coils, plugs for a 2005 350z Roadster Touring Manual

[alkemyst]

Our son was recommended to replace his plugs and coils (they are original). I know the plugs are probably done if so, but not sure if all the coils need to be done. The mechanic told him they probably are not working right (I am sure there is some loss in the translation). How do I test on my own? I did pick up the Nissan Software and the proper OBD2 cable for it.

Working through getting his 350z dialed in (about 130k miles). The car is in good shape, has a couple touched up scratches on the paint but no real dents and dings. Aftermarket single exit exhaust that sounds good and not obnoxious. Replacement Kenwood headunit but only the rear speakers are connected. Top took some work and still dialing that in. Engine compression was good and transmission had a recent clutch (no idea what brand). Mismatched tires.

Had to put in a new Power steering pump, swapped out the pulley setup to the more modern one without the extra idler pulley (both pulleys were making noise). New belts. Brake flush. One of the under dash modules needed to be fixed. Thought it was BCM, but it was another one (his gauges weren't working right). I eventually want to dial in the suspension and get some decent matching tires under (he has the upgraded 18" wheels from the factory).

Don't want to blow money on things really not needed and don't want to buy parts that will need to be replaced soon. He is planning on keeping this car quite a few years.

[VStar650CL]

Change the plugs and then give it a good wringing out on some driver's pavement. You'll feel any glitches if it's misfiring under load. If so, then maybe it needs coils. The only thing that really kills coils in bunches is bad engine grounds, so if you've never had ground issues at the battery or block, make sure it's still good with some voltage-drop testing and leave the coils alone. I've seen lots of Nissans go 250K+ on OE coils as long as the electrical system is well-maintained.

[alkemyst]

That's what I thought. I downloaded the Nissan software and the OBD2 cable. Anyway to see the coil performance there?

What's the best plug to go with?

Thanks.

[VStar650CL]

You can really only see misfires with a scanner, it won't show you things like spark voltage. That takes a lab scope and some special attachments. But performance under load is a fair test, especially if your scanner can read misfire history in the ECM. If the count is zero after a thrashing then you can pretty well assume there's nothing wrong with the coils.

Plugs are a PITA to change on a Z, so my personal preference would be NGK's. They have harder electrodes than Densos and last a lot longer. On the other hand, Densos produce a measurably more energetic spark. Nissan uses both and I'd stick with one of them, not an off-brand. NGK actually just came out with a Ruthenium series that's supposed to outlast Iridium by double. I have one customer using them in a hot-rod Maxima and he's happy with the performance, but time will tell about the longevity claims.

[alkemyst]

NGK for a Nissan (I had a 1998 240SX SE way back) would be my choice, but which one?

[VStar650CL]

Iridiums or Rutheniums. I wouldn't mess with Platinum or Copper anymore even if that was OE equipment, it's dated technology. Fine for a budget lawnmower but not an engine that gets me anywhere. The Rutheniums are pricey, but if the longevity claims are true then it may be the last set of plugs your Z ever needs. NGK isn't known for BS claims, so I'm presuming it's true unless evidence shows otherwise.

[alkemyst]

Agreed ordered the Ruth's. They come in 0.044 so I guess I should have them gapped to 0.040. Ordered an OEM PCV valve as well. Also picked up the Graham Factory Service Manual CD for him. We will dial through the car this year and get it sorted out. It's in great shape, but I am sure especially down below there are some bushings and things to sort out. I know his tires are all mismatched but plenty of rubber on all. I am hoping to be able to do his suspension by his birthday. Not sure on losing the factory black 18's yet, they do look nice on a yellow car.