kimjackson

HI,

I have a high mileage 2009 G37 (173,000)+ I've always kept the car maintained including changing the transmission fluid and all scheduled maintenance. She's been a beauty. Owned since new. In June I had a full tune-up including coils and sparkplugs because I thought it was time - not because there was a problem. However, shortly after, the check engine light came on. Back to have it checked. It registered catalytic converter but the mechanic said he checked both input and output and it was functioning fine. Now, in January, the car failed. I returned to the shop and they diagnosed the coils and plugs on 5 & 6 had failed. Hmmm, He replaced those, charging me for as much as the original tune-up. (almost). The car roared out of the shop. Like new. Now, two days later, it's sluggish and again - the check engine light is on. Any ideas from Inifinity lovers?

BULL

These cars are picky with their coils and plugs.
Unless they are legitimate Denso plugs I would stay away from the any ebay/amazon ones( many documented fake plugs)
Same for the coils, the coils themselves normally stay good, it's the stalk of the coil that ruptures.

It'd be a good idea to check your plugs first top determine the type of them then check their condition. A swap around of coils should tell you if those coils are indeed dead.
Again, check the stalks of the coils to make sure there are no burn marks of spark grounding.

These coils are seeked for their ability to maintain spark past 600whp. So it's safe to say they're pretty robust.

kimjackson

They are Denso plugs... but I did buy them off Amazon...so is it more of a plug issue than coil? Thank you for your repsonse. I love my car and I am disappointed this has happened..

Said Amir

Get some from an auto part or even RockAuto. Some of the ones on Amazon or eBay are fake. That is why it is so much cheaper there than in other places. You can test out the coil packs by swapping them from the good ones and seeing if it fixes the issue, but causes a misfire on the other cylinder you swapped it with. If swapping coil packs does not do anything, then it is most likely your spark plug. Either you got a bad batch, or they sold you some fake ones.

2.2Lude

iTrader: (1)

Fakes are real.

Just trouble shot and resolved this issue on my TL. Car was misfiring only at steady state throttle(think cruise control) but there was no CEL. Reading live data from my scanner I was able to view random misfires on cylinders 2,3,4, and 5.

Did the normal swapping of coils to no avail. Pulled the plugs and the laser iridium electrode fine tips were completely ground down and the plugs looked like a basic copper plug.

I bought some new NGK plugs from my local auto parts store and compared them to the NGKs I had bought on Amazon 4 years/40k miles ago.
Did some research on fake vs real NGK plugs and sure enough I had fakes. Lesson learned.

SkysG37

Ask the mechanic if they still have your original parts.
Swap 'em back in and see what happens.

If they sourced the replacements, and the parts turn out to be fakes and/or faulty, insist on a warranty swap.
You already paid twice.
And they should know better.

If you sourced the seemingly faulty parts yourself, consider it a lesson learned. And be more careful about part quality in the future.

kbrow173

probably a dumb question, but I’ve done it before. Did you clear the code and see if it comes back? Maybe the code appeared while you had the plugs or packs out?

kimjackson

Yes... I did source the parts. Thought I was being smart but guess I should have stayed in my lane lol

kimjackson

Ok - I used Denso plugs of course off Amazon. So maybe I need to get all new plugs and hope the coils are ok

BULL

I would call ASAP and tell him to save your old coils. Most likely at least 2-3 of them are still good and this can get you out of a pickle if you ever blew a coil in the future.

kimjackson

yes, it was cleared and then came back after two days of driving.