# misfire detection



## dnanorton (Dec 8, 2004)

I have a 98 frontier 4x4 with a 4 cyl. I posted in the truck section a lengthy description, but I haven't gotten any help yet. two questions

1) how does the computer sense a misfire.
2) how can a misfire be related to an EVAP emissions system fault.

I have both DTC's Evap fault and cylinder 2 misfire. I have replaced some evap soinoids and sensors, and the plugs, wires, rotor and cap. I don't understand.


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## bowtie420 (Dec 25, 2004)

*heres some help*

The computer senses a misfire by MAP reading and crankshaft rotation balance. No, Evap will have nothing to do with a misfire. Evaproative emmisions sense a fault when there is a leak,(it reads negative atmospheric pressure from the fuel tank pressure sensor) When it senses a leak it will set a p0440 or a p0442 code. A smoke test is a real only way to find a leak, which your dealer could only do. Vent solenoid is usally the only solenoid that has problems, due to water and weather to acces it easily. The Purge solenoid usually is a good part and wont go bad easily. Try wetsoaking the spark plug wires, an look for a spark/light show. I am not very familiar with Nissan vechiles, (i am a Chevy Tech :thumbup: ) If you dont see a light show on that #2 wire, leave another message, i got some other things to try. The only way to really fix something is to understand how it works. hope this helps-


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## luckysperm1 (Dec 24, 2004)

injectors? due to cold weather many o-rings on injectors crack and what not id make sure and check your cylinder 2 injector


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