a year back, my check engine light came on. so, i pulled the codes and it said front o2 and knock. i reset the ecu and no problems. few months later, the light returns and i reset. this went on until 3 months ago, the light came on, but resetting the ecu didn't make the check engine light go away. so, i fork down $250 (including labor) to have both front two o2s replaced and sure enough the light is gone and haven't returned. i check the ecu to make sure no other codes and none found (at the time o2 replacement of the o2).

well, over the last 3 months, i've been experiencing a lot of knocking, especially on the low rpm accerlation. also, i used to get somewhere around ~320 miles to a full tank, now i'm lucky if i can hit 300. most of the time around 280 to a tank. also, the car seems very sluggish lately...not very much fun to drive.

from reading other posts, these sound like symptoms of a bad knock sensor, but wanted to ya'll opinions.

btw, yesterday i pull the code it does list 0304, but check engine light doesn't come on (as expected with a bad knock). no other codes.

and last question, saw a knock sensor in ebay for $99 +4 for shipping. is this a good deal?

you max experts, please help!

 

yeah the ghost code is a good indicator. that ebay deal is the best around so go for it. i need to pick one up myself but don't want to drop the $$ right now.

 

Knock and ping is NOT caused by a defective knock sensor.

Knock and ping is caused by poor fuel grade, excessive carbon deposits, malfunctioning EGR or incorrect ignition timing. To name a few...

I'd look at your EGR system closely, if it's clogged your fuel economy will go down the tubes and knock and ping usually occur as well. The fact that you have excessive knock and ping is whats setting off the KS code. The signal from the KS is probably so high it's out of the acceptable range and the ECU is throwing the code.

 

this was what i was afraid of...

i checked the FAQ on the EGR and it's just linked to pictures and can't tell where it's really located...i can barely make out the general area where it's locted. sorry, but i have no clue what a EGR valve is and does.

i looked up the part and it's only $8, so I'll go ahead and replace it. can you please point me to good written on how to troubleshoot and replace the EGR valve. with pictures would be great, if this exists.

as for excessive carbon deposits, this maybe true since i drove the car with bad o2 for about year. should try one of those cleaners?

as for fuel grade, i always used super unleaded from very beginning. never used anything else.

as for ignition timing, does this have anything do with passing smog in california by chance? back in may, i took my car into a gas station that does the "NEW" california smog test and it failed the first time. the guy said he didn't anything, but add fuel injector cleaner and it passed with plenty of room to spare. i thought i felt the car idling a little higher than before, but didn't think anything of it. could he have advanced the timing to make it pass smog? just guess here...have no clue.

update:
just talked to my mechanic and he thinks it is the knock sensor. according to him, usually EGR problems are also accompanied by erratic idle, stall, and hesitations. as for timing, he says my max in not adjustable, so there goes that one.

and lastly, instead of replacing the knock sensor, he gave me the option of doing something called a knock sensor "by pass". he has done this to many maximas and 300Z and everyone has no problem with it...as long as there is no turbo or supercharger. for naturally aspirated engines, there should be no problem... passing smog is a different story, however.

let me what you think folks.