Newbie on KS?

[justinvw]

Hi there,have got a 95 q45,love the car,its really rare and unique here.but at the moment no power at all! between 2500 and 4000 RPM,after which it flys.got it on a diagnostic device-which read knock sensor faulty.Can I possibly hook up some 550k ohm resistors for a temporary fix?If so,on the 6 pin ks plug,how do the resistors get wired in?The main reason for this temporary fix,is the parts availability where I am. As I understand its not the right way to fix it,replacement is the answer.thanks again.this site is great,cant wait to experience the full potential of the q45 beast!!!

[96Qowner]

Here are a couple threads on the 550K resistor bypass:

G50: Question About Knock Sensor Emulator

'95 Q45 Knock Sensor/Ignition Timing Questions

And page EC-105 of the FSM will give you the pinouts:

Engine Control Section of 1995 Q45 FSM

[Q45tech]

Just subing 550k resistors WON"T unlease the full power since the system must hear normal engine sounds to fully implement the ignition advance.

Kind of a half way fix that won't yield full mpg or power but better than nothing I guess................ALWAYS use the most premium fuel you can find without any safety to protect engine but don't blame us if you trash the motor from unheard knock!

[maxnix]

Go for the fix and avoid the risk of damage.

Kazahkstan?

[justinvw]

Close enough......South Africa.....Thanks for the feedback,been scrolling through the linked FSM manual,wow its pretty scarey!!!

another newbie question.... can the knock sensor throw out performance as radically as I am experiencing-on some steepish hills,get wooried that it wont make it,where my Nissan vg30 pick up hauls out in 4th gear easily?

Regular maintenance has been done to no avail-filters,plugs,oil,there is no water or oil usage,all 8 plugs taken out had a light browny colour. we have 95 octane fuel here.

cheersJustin

[maxnix]

Regular maintenance has been done to no avail-filters,plugs,oil,there is no water or oil usage,all 8 plugs taken out had a light browny colour. we have 95 octane fuel here.

Justin

Wonder if it is measured by the same method?

Something was missed. Might get a cable and a program to look at it as I am sure there are no Consult 1 with the G50 cards in SA.

How are the fluids and filters? Have you changed them all yet?

[qsiguy]

another newbie question.... can the knock sensor throw out performance as radically as I am experiencing-on some steepish hills,get wooried that it wont make it,where my Nissan vg30 pick up hauls out in 4th gear easily?

Yes, I had my car on a dyno with one bad knock sensor and it was down 70-80 hp from normal. Thats pretty significant.

I have my doubts about Tech's comment that you don't get back 100% power with a bypassed knock sensor. I don't claim to be as knowledgeable as tech but I have been deep into the ECU while tuning and know how it responds to knock input. There are maps for "No knock" and "Knock". There are no maps for sorta knock, questionable knock, or suspicious knock sensor. If it senses no knock it uses one fuel and timing map and if sees knock then it has a separate knock map for fuel and timing. It's on or off, no in between. If there is no knock code recorded in the ECU it will be running on the No Knock maps.

I would love to learn how you only get some improvement from a knock bypass Tech if you have a concrete explanation for it. Not trying to prove myself right, I really want to know how this could be as I am still trying to learn everything about what makes these ECU's tick since I'm still tuning my car.

By discussing this I am not saying that I recommend it for more than a very temporary fix nor that it is safe to run this way very long. I am merely debating the results of a bypassed knock sensor as far as how the ECU sees it.

[Q451990]

I have my doubts about Tech's comment that you don't get back 100% power with a bypassed knock sensor.

Check out this thread...

zerothread?id=228166

My guess is that he compared the timing advance at WOT with the bypass vs. functioning KS.

Heath

[qsiguy]

Well as usual that is very complex "text book" answer from Tech regarding how knock sensors work. Still, I have seen all the code that exsists in the ECU programming and there are no partial maps. There is a knock map and a no knock map for fuel and timing and it only access the knock maps if it detects the knock sensor signal or if there is a problem with the sensor. If there is no knock fault code showing up nor any knock it's not accessing the knock maps as far as I can tell. I can see in both fuel and timing maps where it looks for knock and can also see where the ECU makes changes when it sees knock. It's binary, on or off, and it only looks for knock in certain areas of the maps.

[bullittandy]

Yes, I had my car on a dyno with one bad knock sensor and it was down 70-80 hp from normal. Thats pretty significant.

That's alot of H/P!!! No wonder people love their cars after getting the K/S fixed!

[sdkhalsa]

I used the 550K bypass where one of my KS's was out. It worked great. My situation involved the KS being open(not shorted), so putting a resistor in parallel with the original was very simple and effective. I don't think you have to get very philosophical about this because you invariably find yourself needing to pull the plenum for some other reason, typically fuel injectors, fuel hoses, or coolant leaks, and you can do the KS's and harnesses properly then. Ideally you would take care of all the under plenum work at one time, but this is expensive and time consuming. I have made three trips in over the last four years.

[PachoC]

On the original question on how to wire the resistors.... I am not an expert but by looking at the 6-pin connector, I guess it could be done as follows: - connect a piece of wire to white cable (going to the KS that is not working- add an in-line fuse holder + an appropriate fuse to this cable- add the resistor(s) to the same line, but after the fuse- ground the end of the line (somewhere on the engine)

The fuse should protect the ECU in the event the line gets shorted...

Again, I am no expert here....

[qsiguy]

A fuse won't do anything to protect the ECU. You are supplying the ECU with a ground signal through the resistor. You are over complicating it.

What I have done is connect a wire to ground to one side of the resistor and the other side of the resistor to the wire on the ECU. Most may not want to cut a wire near the ECU but I did since I am not intimidated by wiring at all. I just grounded the wire near the ECU.

You could do the same thing out under the hood. Unplug the knock harness and wire a resistor to the wire leading to the ECU and the other side of the resistor to ground.

[PachoC]

qsiguy - Tks for the explanation. I thought the fuse would help in case the line going to ECU was accidentally grounded before the resistor, but again, I am not an expert on this stuff.

Justinvw- I guess you now have the information you were looking for.

[Q45tech]

Just remember that the KS only listen to the bank on which they are mounted so the resistor substituted bank will be totally unprotected and if that one bank is the knocker well time for new crank bearings and an engine rebuild if you stress the engine without knock control.