sky jumper

There seems to be a general misconception on here about how the KS system works. most people think the ECU is constantly searching for the optimum ignition timing by advancing it until the KS senses knock, and then backing off a bit. That's not how it works.

The KS is merely a fail safe mechanism to protect the engine from knock caused by using low octane gas. That's it. The KS is not used to optimize performance in real time. The ignition timing map is pre-programmed not to cause knock so long as premium fuel is used.

from page EC-24 of the FSM....




so then - what if the KS fails?? the ECU then reverts to a "safe" timing map to prevent knock even with 87 octane. this is why a bad KS does not trip the CEL -- because it really isn't a problem - the engine is safe and will run just fine.

but how does this "safe map" affect performance?? it really doesn't, IMO.

When I changed my KS I did quite a bit of live on-road testing using an OBDII scanner. I recorded the ignition advance under various conditions both before and after the KS was replaced and ECU reset. there were only 2 conditions where I noted an obvious difference in timing:

1) under very hard acceleration at high RPM (>4k). in this case, with the faulty KS, ignition advance was limited to single digits (between 3 and 8 deg). with the good KS it varied between about 7 and 18 deg. with the butt dyno I could not feel any difference in power or acceleration whatsoever.

2) highway cruising at low RPM. good KS: 35-48deg. / bad KS: 20-25deg.

for all other conditions (light to moderate acceleration, low to medium speed cruising, cold start, etc) I noticed no difference in timing. it should be noted that ignition advance bounces around quite a bit, and the best I could do is record ranges at various operating points.

What about MPG?? personally, I noticed no improvement in MPG after I replaced the KS. it does stand to reason that at highway speeds the engine should get better MPG on the "normal" ignition map, but I just haven't seen it.

Bottom line - don't expect a new KS to give you any miracle cures to low power or low MPG. it was designed as a fail safe to protect the engine - but there is very little difference between the "normal" timing map and the "safe timing map".

andrei3333

i have had the 0304 code for KS but started using premium fuel for the past several weeks, its been freezing so i did not check the ecu for codes again, do i need to change my KS ?

a dealer told me since i bought a used car and dont know what gas was put in it before, use the car until the KS simply fails and then replace it and the only use premium fuel, is this a valid option ?

l3ftonm3

iTrader: (2)

I would check for codes once again if you reset it, since the KS is a ghost code sometimes. Reset ecu drive like 200 miles and check. If it comes up might as well replace only 75 bucks for one.

sky jumper

switching back to premium will not get rid of the KS code. like l3 said, reset the ECU, drive a bit, and then recheck. if the code is still there then your KS is faulty. (just take it to Autozone and have them check/clear the codes).

as for running only premium after you replace the KS -- personally, I believe that is good advice. I have a background in piezoelectric device R&D and I can tell you these things are very fragile. no reason to subject them to more shock & vibration than necessary (which is what 87 octane gas will do).

andrei3333

autozone is unfortunately an american only service department, here in canada not a lot of shops do electrical work, and its $100 dollars to check it with a computer at the dealership

i also dont have a torque wrench and even if i get into the manifold and somehow reach the KS i would not be able to tighten it to correct torwue setting (if i decide to change it at all)

buzpuck11

iTrader: (3)

Torque the KS to hand tightened and then another 1/4 to 1/2 turn. It is not hard to change. Buy some a socket, extender, and U-joint if you don't have them, then return them when you are done. Should take you a 1/2 hour at most.

Sounbwoy

iTrader: (2)

I hope you realize the can of worms you've opened! But I'm on your side and I'm no scientist.
There are tons of people who swear they felt a big difference when they switched the KS. I'm not among them. My mileage didn't increase nor did I get a dramatic increase in power. At the time, I had a bad KS AND a completely clogged EGR pipe. I was still getting 25 to 28 mpg in combined hiway/city driving with some of that on regular gas....

sky jumper

oh I realize it -- in fact that is precisely why I started this thread... to set the record straight on how the thing works. there's a simple scientific explanation for all those claims of big power and MPG gains - it's called the placebo effect, and it has been systemically reinforced by a deep rooted misconception of how the KS works -- if you believe it is an intelligent, real time performance optimization device, then surely your car must run like crap if the thing is broken. and when it's replaced, surely the car runs better/stronger.

also, in many cases people replace several components along with the KS (like O2 sensors - which will have an impact on A/F and thus power and MPG) but wrongly attribute any improvement to the KS.

wetzelman1

iTrader: (2)

I just replaced mine and felt a huge difference along with most people. I'm not claiming that I got a huge power increase but I could defenitely feel the difference. I remember the instant that my engine knocked for the first time and the knock sensor went bad. My car immediately started accelerating differently. From then on, my car would hesitate during acceleration in second gear. My car would start to accelerate, then it would feel like the accelerating would"skip" for a second. As soon as I replaced the knock sensor, this hesitation was eliminated.

I think that saying replacing a bad knock sensor does nothing is far from accurate. Their is a misconception that the knock sensor increases power whereas I perceive that the increase is in overall car performance.

2da mizzax

iTrader: (4)

and then......

MOHFpro90

iTrader: (11)

Sky jumper, ask a mod to put this into the Stickies(FAQ or something), it deserves it. Common misconceptio I would totally agree, I think more people need to read this, taught me.