Car sounds and shaking/misfiring(?)

Bought a 2011 infiniti g25 a month ago, ran fine. Past 2 weeks it idled roughly (more so in D and R) and would jerk, also during braking. I’ve tried a couple things so far already :

  • Changed all 6 sparks
  • Cleaned both MAF (gonna try again)
  • Cleaned both Throttle body
  • Replaced ripped left rear intake hose
  • Checked battery
  • Correct 91 fuel
  • Oil change

Just today it got worse, was driving around and my engine light came on, started blinking, car started buzzing and shaking, and ever since, the idle has been so noticeable that cups in the holder have been hitting the sides. Just got out the car after work and I heard some ticking noise I hadn’t heard before, or at least it wasn’t so noticeable. I did chang my spark plugs yesterday, but they’re compatible and the car ran just fine towards work in the morning. The rough idle is more noticeable in drive/reverse and i do know that my OBD had the engine cylinder 6 misfire code and live data showed STFT Bank 2 at 10-13% Average, with Bank 1 at 3% Average during idles. Need some advice or suggestions.

Edit : Forgot to add, the engine light stays on the entire time, but driving to 35-40 specifically makes it blink. Not sure if it’s important. Stops blinking after and doesn’t blink while braking, just hitting 35-40 strictly while speeding up.

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A flashing / blinking check engine light indicates a misfire, don’t drive the car in this condition. Unburned fuel dumps into the cat converter and ruins it.

I think you figured out why the car was sold.

Have the codes read (check engine light) and post them here. The code format is P123x

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The OBD indicates a misfire on #6 so as a start that’s the place to focus on.
Three years old is still pretty new but you didn’t indicate the mileage

When you changed the plugs how did the plug on #6 look? Wet? Dirty?
Are the plug wires and wires to the injectors all clean, flexible and tight?

If so and you’re lucky, it may simply be a clogged or broken injector.

It’s a 2011, makes it thirteen years old years old.
My manic eight ball predicts a P0140 code in the near future.

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Move #6 ignition coil to another location

Drive the car until it acts up again

Has the misfire moved with the coil?

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Swapping ignition coils is cheap and easy. Since this model does not have Direct Injection, you could also swap fuel injectors, however you would need to be super-careful to ensure that this does not result in a fuel leak, or dirt falling into the engine.

However, the fact that this problem is accompanied by loud ticking noises tells me that it is probably a valvetrain issue. And unless you are able to DIY, major engine repairs will likely exceed the value of this car.

+1
Does the OP have maintenance records to verify that the correct spec/viscosity oil has been used in that engine? If not, there could be damage to the VVT mechanism, and I suspect that this would not be cheap to remedy.

Recently changed the spark plugs, a slight bit of oil on some spark plugs but before the change, the car only had small misfires, enough to feel but not turn on the lights or send a code. The coils seemed normal, though coming from a first time driver. Taking my car to a mechanic sometime in a week.

Not sure where to find it, I could go through the papers I was given to check or anywhere else you might suggest.

Will try this out when I have the time, haven’t had any recently.

If it’s dangerous, I’ll leave it to a professional, I’m still new to any of this and don’t want to mess up anything. Will ask the mechanic I go to of this idea when I see them.

I dont know how severe any ticking is, I’ll say though that the ticking comes from under the car and not the engine. If I’m able to upload videos or audio (not sure how), I can get a sample and upload it

Wonder if timing chains are/were worn and seller put in a cheap set? I’ve heard that some cars are really picky about Oem chainsets.

… which could be another indication of a lubrication-related problem.
From afar, we are all guessing, but I think that the OP probably bought a car that wasn’t properly-maintained by the previous owners (a 13 year-old car could have had several owners).

2 Owners, but bad maintenance is what I’d assume as well.

When a misfire occurs after replacing the spark plugs, inspect the coil and spark plug for the cylinder that is misfiring. Worn timing chains and VVT malfunctions will have different symptoms.

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Could you tell me what symptoms would differ from timing chains, ignition coils, and VVT?

Suggest to focus your att’n on getting the misfire on 6 fixed. That may solve the other symptoms.

Do you have access to the car’s recommended service procedures?