I have a 1996 pathfinder the mechanic say the knock sensor is bad what does that have to do with the emission?

Answer 1

Knock sensor is used to determine ignition timing.

Bad ignition timing = poor emissions control.

Many cars these days are built with higher compression engines to take advantage of the higher octane fuels. Higher compression means more power, but manufacturers realized, many people are cheap and don't want to pay for the more expensive gasolines. So they put in a knock sensor.

The knock sensor informs the comptuer when to send the electricity to the spark plugs for optimum fuel burn, but without engine knock. So with high compression engines with high octane fuel, the fuel is ignited later than if you use the cheap octane fuels (where the knock sensor would retard spark)

A bad knock sensor would give an incorrect timing to the computer as to when to send the electricity to the spark plug or it's probably in open loop mode, meaning it's just using the default mode when the knock sensor fails and thus releasing more emissions than it would if the knock sensor was working.

Answer 2

That year the sensor is under the intake manifold. It does not turn on the check engine light. If you use good name brand fuel everything will be ok. If you shop at low price fuel stations get a new knock sensor. The only effect on emissions is higher than normal NOX2 oxides of nitrogen. And of course if engine pings to much engine damage.

Answer 3

Your knock sensor is an ecu input that tells it when it's not running the way it should(pre-ignition or detonation). With that information, your ecu adjusts accordingly. When you get a false input, your ecu will default to a rich condition(high emissions). Late model cars are tuned to run lean for low emissions purposes, but when a false input is seen by the ecu, it will default rich because rich mixtures are much safer and have less chance of any catostrophic engine damage.

Answer 4

Not much with emissions,but will effect engine wear and possible damage if engine pings or knocks. The knock sensor detects a pre-ignition and will slightly retard the timing to eliminate this condition. Has your engine been knocking?

Answer 5

Because the engine is computer controlled and this sensor is one of the inputs for engine timing. Therefore the law reads that all these items need to be in good working order to pass the emmissions testing.

Answer 6

The knock sensor is what controlls your emissions.

Answer 7

i own a repair hop,and it makes it not fire right ,this means its not burning the gas right which increases the emissions on it this will make it run really bad also,at times,if he said it was bad it probably is,,you can try changing it,,and you may notice a big change n the way it runs,,or you,ll at least see a difference in the gas mileage on it,,good luck hope this help,s.happy new years.