The engine idles rough at stops and low speeds?

2019 NISSAN FRONTIER
39,000 MILES • 4.0L • V6 • 2WD • AUTOMATIC
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FIREMAN305
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When changing gears from park to reverse the car vibrates. In neutral in smooths out and in drive in vibrates once again. MAF sensor went bad and was replaced once the check engine light came on. Changed the PCV valve that was failing causing the MAF sensors to be damaged. Changed the original spark plugs and coils (original plugs were not gapped properly to 0.044). The car smoothed out and the vibration stopped. The 2nd time the MAF sensor was changed the car once again started having vibration issues once again at idle. The only codes present beforehand were P0171 and haven’t come on since changing the MAF sensor. No codes now but car is having rough idling.
Feb 23, 2025 at 9:59 AM
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STRAILER
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To confirm this truck has 39,000 miles. This truck must have the correct spark plugs at the right gap.

NGK Iridium IX with the part number ILZKBR7B11

gap: 1.1 mm

A rough idle condition can be a vacuum leak or low compression in one or more cylinders.

https://www.2carpros.com/articles/repairing-engine-rough-idle-issues

The P0171 code indicates that the engine’s computer has detected a lean condition on Bank 1

This can be because of a misfire @ idle. I would check for vacuum leaks first which is easy to do. Use this guide when the engine is cold:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please go over these guides and get back to us.
Feb 23, 2025 at 12:18 PM
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FIREMAN305
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Yes 39,000 miles. The spark plugs I took out initially were all gapped at different measurements. I used a wire feeler gauge, and they were at 0.030-0.044. I took the car to the dealer and all they found was a small leak in a hose but other than that no findings. I have done the smoke test and no leaks were detected. Will check the brake booster hose although have had no issues braking thus far. Have used Lucas fuel injector cleaner and have cleaned the throttle body. Short- and long-term fuel trim values have improved since replacing the failing valve. The values are fluctuating. The long-term values are at 0 when accelerating but go up and down when idling. At idle the STFT for bank 1 is 8.4 and bank 2 is 4.3. The car has never turned off or stalled. Has never had issues starting.
Feb 23, 2025 at 5:43 PM
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STRAILER
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The STFT for bank 1 is 8.4 and bank 2 is 4.3 seem off, they should be closer to the same. It does sound like a fuel injector issue so the cleaner might help. When you removed the spark plugs was one of them dark in color? This will be the cylinder that is having an issue.
Feb 24, 2025 at 11:01 AM
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FIREMAN305
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Sorry for the late reply. After having some free time to address the problem. I removed the fuel injectors and used a tester. Injectors 3 and 5 were partially clogged. Sprayed with difficulty. Got them cleaned and now the issue went away. Smooth idle now. Thank you and appreciate the help.
Mar 8, 2025 at 3:41 PM
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STRAILER
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Nice work! Use 2CarPros anytime, we are here to help. Thanks for letting us know, please tell a friend.
Mar 10, 2025 at 9:18 AM