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Nissan Sentra Failed Inspection

Q. Hello, I'm writing about my 1994 Nissan Sentra 1.6 liter. My car recently didn't pass the emissions test. They said it was burning excess gas, it read 1.15 on the HC and should have been .85. The car when it's idling, accelerates on it's own and then calms down and then accelerates and etc. I noticed when I press on the gas pedal to rev the engine, black smoke comes out.

Nissan Sentra Failed Inspection

Not a lot, usually at a high rpm enough for me to notice it. I took it to the shop and they changed the catalytic converter, spark plugs, PCV valve, O2 sensor, fuel filter, oil change, rotor and distributor cap. After that the car started again.

Also a friend of mine, who is a mechanic, told me to spray throttle cleaner. It helped for a little bit, but the funny idle started again. The car runs fine once I reach a good speed, but once I come to a stop, the idle lurches.

Also when I'm on the highway, around 25 mph and up, it takes time for the engine to respond when I press the gas pedal. Maybe it could be the timing? Please help, I'm up for any suggestions. I'm afraid to take it to the emissions testing and not pass again.

Thank you in advance!


You are not that far off. First thing I would do is put in a set of NGK BKR5E-11 gapped at 0.039" to 0.043". That in itself could very well bring you to specification. Nissans do not like, nor will run efficiently, on any other kind of spark plug.

Also, the throttle cleaner doesn't do too much as far as cleaning. What you should do is give the throttle a good cleaning by hand.

DIY: Cleaning Throttle Bodies

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