is my knock sensor bad

Discuss topics related to the VQ series engine.
nstymax
Posts: 1
Joined: Sat Nov 21, 2009 1:06 pm

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I have a 02 maxima. It has a knock but its light, i use only sunoco 93 and have for two years i owned it. I noticed if i have to change gears and lean into it the car hesitates for a split sec then goes, but if i wind him out, sometimes he wont give me all he has, almost like its starving for fuel, people told me thats the timing retarding but i have no check engine light. the pinging i hear is very light but noticeable when at low rpms especially if i give him some gas and dont shift up. has 93k but nissan replaced motor at 58k under warranty. im told they replace the bottom end but put all the other stuff back on from original motor. please help me with this, and if its knock sensor, is it exspensive to rreplace? also heard it might be mass airflow sensor. nissan says knock sensor never goes bad, but this guys a sercvice writer, not a tech. not real sure how to retrieve responses so if you read this and can send a reply to my email, I would be forever in debt, its [email protected] dont know what to do or how to begin to fix this, so far im told its a knock sensor, thats why when it pings it retards timing, if thats it, why no engine light? thanks for the help guy, Nick.


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Infinitiguy19
Posts: 7787
Joined: Sat Dec 22, 2007 4:58 pm
Car: 1993 Infiniti Q45 188580 Miles
1994 Infiniti Q45a 240000 Miles

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Knock sensor fail over time because of heat (10 years) or nearly instantly in say an engine overheat because of a cooling system problem. When the knock sensor fail the ECU then reverts to a more retarded timing to protect the engine. So if the ECU brings up the Knock sensor code then more often than not its right and they should be replaced. Retarded timing=less power...

Q45tech
Moderator
Posts: 14365
Joined: Tue Apr 30, 2002 3:19 am
Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl

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Normally a KS code occurs only when each KS FAILS the initial startup resistance and background noise test.

The engine is constantly being adjusted by KS signal. The ignition is advanced until mild knock is heard by KS then backed off in increments until the knock is stopped then the whole process starts over again 5 seconds later.

Actually hearing knock means the KS system has reached its preprogrammed limit and can't do any more.

Find the problem such as piston/valve deposits or ring wear letting too much oil into combustion chamber or low quality fuel [the marketing octane sticker is set by station not the refinery].


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