knock sensor
 

Would a knock sensor code affect the acceleration and gas milage on a vehicle, maybe it would change the timing on the vehicle. If someone could let me know that would be great, i know knock sensor cost money, for the part and labor so i just want to know if it is worth changing. The code comes of and on, one day it would be on and then the next day or maybe a few days later it would be gone. I would appreciate it if someone could help me out, thanks guys

RE: knock sensor
 

bottom line is yes, you lose power and also you will consume more fuel. if the sensor actually encounters knock, the ecu will pull timing. if the motor is a 2.3, i bet it will also limit boost. if the connection to the sensor is bad, or if the sensor itself is bad, i think the ecu goes open loop, so it reverts to factory default maps, which mean less timing, and if a 2.3, less boost. also richer fuel.

RE: knock sensor
 

Agree completely with that. I do not find any information about what the failsafe is for the knock sensor but would imagine that the spark timing would be retarded to some degree and probably even fixed which would create the hesitation and lack of power. Would not expect starting ability to be changed though. Not quite sure am understanding exactly what the starting problem is. Does it take longer for the engine to start cranking over when key is turned to start position???

RE: knock sensor
 

No it starts to crank over right when i turn the key, its when it is cranking over it feels and sounds like its gonna die, then the car would turn on. Now it does not always do that, sometimes i start fine, ill turn the key it would crank and then start right up, but then there are those times were it does what i said. And also Can you tell y my CEL comes off and on, y doesnt it just stay on (knock Sensor). Thanks for your help guys

RE: knock sensor
 

i would guess the ecu is actually hearing knock, or, the connection to the sensor is being interrupted. when the ce lites, it is probably making the adjustments because of knock, and throwing the code. when the lite goes out, probably because ecu no longer hears the knock, BUT, there may be a time/mileage that the car must go before ecu will release it from the knock mode, iow, even tho the lite is out, timing/boost may still be pulled until the ecu is convinced it is not a problem. the galant would hold it in knock mode for 200 miles AFTER it went into knock mode. the only way to remove that was to disconnect power to the ecu and erase memory.

RE: knock sensor
 

well i just had another think hit me, do you think that i need to change the timing belt?

RE: knock sensor
 

Doubt that a timing belt is going to create the long crank time condition. Once a belt jumps a tooth then odds are about 8 billion to 1 that it would correct itself iintermittently. A collapsed hydraulic tensioner for the belt might allow excessive belt flex that could throw cam/crank timing off howevevr. Would not cause the knock sensor or CEL.
The reason you are probably seeing the light on and off is that the PCM is constantly looking at the voltage ouput to the knock sensor. If the voltage goes below 1.25 volts or above 3.75 volts due to either a shorted or open sensor or circuit then it will turn on the CEL. If voltage goes back to normal then CEL will be turned back off. Have seen this myself on a knock sensor. Went to check resistance and found resistance ok. Walked over to get service manual and rechecked and now sensor was open circuit. Just the way some sensor start to fail. Will probably completely die if left alone for long enough.
I suppose you could try and fool the PCM into thinking the knock sensor resistance was normal. Never tried this so do not know if it will even work. .Normal resistance of the knock sensor is listed at 560,000 ohms. Might be possible to get a resistor that matched at electronics store. Use a jumper wire to connect one end of resistor to unplugged knock sensor wire and other end of resistor jumper to engine ground. Might work to see if that will at least see what problems the sensor might be causing anyway.

RE: knock sensor
 

hey babyheuy, about the timing belt i was asking that if it would be the cause of my lack of acceleration. Something is up cause just last night my car would not start, the lights would dim and the starter was clickin, i turned the key again and then the same thing nothing but the starter and i tried it one more time and then it started like nothing was wrong, well i turned it off to see if it would start and it did not the first time and then i tried it again and then it started again like nothing was wrong and it never did it after that. You think something might me shorted out? i would have been better off buying a bicycle than this car!!