How do know when it's time to change spark plugs

teemoney

teemoney

Member
Location
Toronto, Canada
Car
2007 Infiniti fx35
Just wondering if you guys just go with what your mileage says or did you feel the car drove different. Reason i ask is when i start the FX in the cold it stumbles on low rpm's then seconds later it'll idle where it should and drives perfect throughout the day. When it hot outside it doesn't stumble upon startup. I am currently just over 80K miles. Is it time to change plugs or is it something else?
 
teemoney said:
Just wondering if you guys just go with what your mileage says or did you feel the car drove different. Reason i ask is when i start the FX in the cold it stumbles on low rpm's then seconds later it'll idle where it should and drives perfect throughout the day. When it hot outside it doesn't stumble upon startup. I am currently just over 80K miles. Is it time to change plugs or is it something else?
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If you are still on the stock spark plugs, then yes, now would be an excellent time to change them...

Spark plugs are exactly as you say, mileage based. Unless something goes wrong with them or you have problems with them there is no reason to replace sooner than necessary. On the other hand it is a cheap and easy piece to replace, and hard to tell sometimes when they are not working as well as they should so many will replace at the 50k intervals or 60k intervals.
 
Reminds me I should do that soon, I'm at 95k.

You can also see if you have oil on them to see if your valves are leaking.
 
It could be the plugs or something else. But at 80K, you might as well change the plugs and see if it fixes your problem. 100K is the schedule I think. It will be the cheapest thing to start with. Replacement interval depends on more than just mileage. I replaced mine at 46K and there was a huge difference, but all of my miles are in the city, short trips of under 10 miles, sometimes under 2 and lots of redlight racing to get around people. $50 and an hour of your time isn't too bad even if it doesn't solve your current cold start problem; it can't hurt.
 
Thanks for the replies gentlemen. Shadow i do mostly city driving as well. I guess i will change them, lucky for me the NGK Iridiums are on sale at my local auto store. I will change them in the next week then. I hope i don't see any oil on the plugs when i get them pulled
 
Look for oil inside the spark plug well with a flashlight before you pull them. If there is oil in there, you need new valve covers (or at least replace the seals).
 
On our FX, the seal around the spark plug wells is not replaceable. It is pressed and sandwiched between the inner and outer layer of the valve cover. A new valve cover and valve gasket is around $150 - $180 will be needed if there is oil in the well.

Someone or company did a replacement seal, but it requires you to use a hole saw to enlarge the existing hole and then reseal it. I would suggest to spend on a new replacement rather than someone rig up a replacement for such important part. Plus if you paying for someone to do it, if the replacement seal route fail, you will have to pay for the labor and parts again.
 
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I have never cleaned or checked my throttle body. I was getting the same issue when startng last winter but again it went away when summer came around

My cousin seems to think it's normal but it wan't happening when i first bought my FX
 
If it were me, That would be the first thing to check. easiest.
Just be careful cleaning. So sensitive, that if you breathe on it the wrong way may have to do a position relearn using the pedal method
 
i would change the spark plugs, clean the air filter, clean the tb. and clean the upper and lower plenum . guarantee you will feel a difference.
 
I think it's time for a tune up. Will have everything mentioned done. My FX is in great condition but not sure if the previous owner took good care of her. When i bought it the ac belt was missing and the main belt had cracks. The dealership did replace then when i bought it. Don't we just buy new air filters not clean them?
 
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