# Rough idle issue?



## Eric_B_1984 (Apr 6, 2014)

My girlfriend has an 06 Altima 2.5, she says around March or April of last year she had the spark plugs replaced. When you're sitting with your foot on the brake in gear, it recently started idling rough. It doesn't do that when the car is in park or neutral. She told me that the car was doing the same thing before she did plugs in the a year ago, but it seems that it shouldn't need plugs this soon. About a month or 2 ago, it threw a code for P0420 Catalyst Efficiency Below Threshold. But went out about 3 days later, and hasn't been on since.


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## rogoman (Dec 16, 2004)

A P0420 code is generally caused by one or more of the following conditions:

- Three way catalyst (manifold) defective
- Exhaust pipe leak
- Intake system vacuum leaks
- Fuel injector dirty or leaks
- Spark plug fouled
- Improper ignition timing

Make sure you're using the proper spark plugs; they should be a {PLATINUM-TIPPED type) NGK PLFR5A-11 plug. The replacement interval is 105,000 MI. Any other aftermarket brands can cause unreliable engine operation.


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## Eric_B_1984 (Apr 6, 2014)

Yeah, you pretty much confirmed my thoughts. I am thinking that whoever did the plugs (before I met her) just put whatever was on sale in it. I haven't pulled it apart yet, I have next week off, so I'll do it then. From Sheridan Nissan in Delaware, the plugs are like $6 a piece, so I say why screw around, just get them there. It's not that expensive.


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