I recently bought a 2008 g35xs sedan with automatic trans. As far as I can tell from the car fax and information I received the spark plugs have never been changed. Should I be worried the engine has any permanent damage from the plugs maybe breaking off? It sometimes feels like it has a slight shake or wobble coming from the engine usually when cruising at around 2-3 thousand rpm. I also noticed a slight ticking feeling coming from the gas pedal above about 1700 rpm. It isn’t a very
aggressive feeling but definetly noticeable.

 

You definitely need to replace the plugs if you think they have that many miles on them.

Make sure the engine is 100% cold never been started that day. The only time I've broken plugs off on modern engines is when the engine wasn't cold. Apply a small amount of anti-seize to the new plugs, don't get any on the 3 threads closest to the combustion chamber.

 

Nissan says to change the plugs at 105k miles so 116k miles isn't a tragedy. I changed mine at 120k only for "maintenance" reasons. Had no symptoms, fuel economy didn't improve with the new plugs, etc. Even the gaps on all (6) plugs were still in spec !! That said, plan to change them. Use 'stock' Denso or NGK Iridium plugs. I wouldn't worry about breaking them off either, especially if you think the mileage would be an issue. Follow the advice cleric670 gave.

 

I'm almost at 105K and independent shop has told me they can last much longer, debating whether to change them (may let them decide). So you didn't notice any change in performance after changing them?

 

Just replace them if they have that many miles. No sense waiting for it to start throwing a CEL. They affect fuel economy and performance pretty substantially.

 

Just picked up a 2008 G35S yesterday. It has 141k miles and I can't find anything showing the plugs have been replaced yet. Has me a little worried one what else I need to be looking at replacing at this point that might have been missed.

 

The maintenance schedule for the 2006 is basically the same, this will let you know what the service intervals are for various systems, you may still have the maintenance schedule for your vehicle in the glove box they shipped one with all new vehicles.

https://static.nhtsa.gov/odi/inv/200...067-41185P.pdf

As for components prone to wear that might need to be serviced, obviously the spark plugs is a major one, pull one plug and inspect the gap, that will give you an idea what the other 5 are like. Personally I would just replace them all with the factory plugs.

Random suspension components are usually pretty worn by that mileage, struts/shocks, wheel bearings, tie rod inner/out, lot of suspension bushings on the front multi-link setup, rear differential bushing is definitely shot unless it's already been replaced, most folks opt for a polyurethane bushing because the factory rubber filled one is prone to early failure.

Take your car in for an alignment at a local REPUTABLE (i.e. not firestone) alignment shop and if there's anything at the failure point on the suspension it will prevent them from aligning the car and you'll know.

Check the date stamp on your TIRES, it doesn't matter how much tread is left, if they're 5+ years old you should start shopping for replacements.

A lot of this stuff can be done at Nissan/Infiniti if you just take your car in for an oil change they will give it their multi-point inspection which will tell you a lot.

 

That's exactly what I planned to do. Take it to the Nissan dealership for its first oil change and let them tell me what needs to be replaced. Thankfully alignment was done recently and tires have less than 5k miles on them. Brakes and rotors were just replaced. Spark plugs I can do myself. I do think the struts/shocks need to be replaced soon as well.

 

What's the stock part number? I can't find the part numbers anywhere.

 

Do you not have the owner's manual? The factory service manual lists Denso FXE22HR11.

 

Preparing to do the plug change. I have the Denso plugs in hand and wonder whether I need to set the gap on the plugs or is the gap already set? Anyone know the gap off hand?

 

Gap is factory set on platinum and irridium plugs. You can check it with a feeler gauge set or the spark plug wheel but do NOT bend against the electrode on the plugs it will bend VERY VERY easily. They do make a tool to bend the ground strap of the plug to open it up if needed, to close the gap just lightly tap the ground strap on your work bench.

Normally you do not need to make any adjustment whatsoever though.

I think the plug gap is still 0.043 inch on the HR motor.

EDIT: You don't actually need the specialty tool to open up the gap on plugs, you can just grab the ground strap with a pair of pliers and bend it back slightly, however you don't normally need to change the gap on a new set of plugs.

 

Thank you very much for the valuable information!!