I have a quick question, Once you replace Knock sensor, after how long you can start feeling the difference. I took my car to AutoZone, the guy hooked up his hand held computer and the only error on my car was " Knock sensor Maulfuntion" I just replaced it today. I was just wondering. Thanks

 

A few days or couple hundred miles. Then again you might not notice any difference at all.

 

Did he reset your ECU?...I felt a huge difference, drive your car hard and you feel a difference in about 2 days.

 

i felt it once i reset the ECU, i could chirp immediately, which i couldnt do before, could be in my head htough, but my gas mileage went up immediately, from 14 to 19

 

And how do I reset ECU?

 

Its in the FAQ

http://forums.maxima.org/showthread.php?t=104931

 

I felt a difference immediately. It was like night and day. It depends on what octane number gas you're using, though. If all you burn is 87 octane, then you won't notice hardly any difference, because the ecu will retard timing when the new knock sensor detects detonation. With 89 octane you will probably notice some difference, probably not too much, but with 91 octane or higher there should be a significant difference. That is, if your old knock sensor was truly bad.

 

Do they charge yout to check for codes at autozone?

 

you should feel the difference immediately regardless of what octane you are running. I have done this twice with 87 octane and 97 and both times I felt the difference when I flored it.

 

Sometimes my wife puts 87 octane in her 5th gen, and I immediately notice the difference in power. It feels like my 4th gen did when it had a bad KS. The most noticeable increase in power after replacing a bad KS is in the mid rpm range and at partial throttle. That is when the ignition timing is advanced the most and is most susceptible to knock-induced timing retard. Some knowledgeable people here maintain that the ecu doesn't use knock sensor information at WOT but reverts to timing tables based solely on rpm and airflow. The FSM does hint at that without really saying so.

 

Nope, it's free. However, it's not a diagnostic machine that they use ... it just pulls your ECU codes and they tell you what to buy from them

You can find OBD-I and OBD-II scanners on the internet. Some even come with really nice software for your PC so you can do running diagnostics on your car as well as pulling/resetting codes.

Here's a few links if you want your own (very worth it IMO):
http://shop.store.yahoo.com/rodi/autxrayezobs.html
http://www.obdii.com/
http://www.mobileplanet.com/product....pf_id=MP181503
http://www.dervman.com/obdii.htm

 

i agree grade of gas plays a large role in it.
when i changed mine i know for a fact i had super in it and the difference was incredible. since that time i know my wife has put 87/89 in it and it is still improved signifigantly but performance has dropped. i would not go as far as to say running 87 is similar to when you have a bad knock sensor, no knock sensor is much worse performing than 87 with a good KS. the improvement is just gonna be less obvious.

by the way, my improvement was immediate after changing KS. i changed it, reset my ecu, and HELLO.