Bypassing knock sensor

AbsoluteGTR · #1 11-10-2006, 05:41 PM

How do I jump/hard wire the knock sensor? Can I do it by just unscrewing it and/or unplugging it?

I want the ECU to not read the knock therefore not pull the timing.

I know this is not good, but it would only be like this for like 10 minutes.

MT-2500 · #2 11-10-2006, 05:52 PM

Quote:

Originally Posted by AbsoluteGTR

How do I jump/hard wire the knock sensor? Can I do it by just unscrewing it and/or unplugging it?

I want the ECU to not read the knock therefore not pull the timing.

I know this is not good, but it would only be like this for like 10 minutes.

Well for a 10 minute test just unplug it if you can find thee plug in.
Your check engine light may come on and the code will need cleared after you are done checking it.

AbsoluteGTR · #3 11-10-2006, 10:43 PM

Thats the thing, the purpose of me jumping the knock sensor is so my ECU will not change my timing and I want to see, by jumping it, if my car is suffering from knock, because it so incredibly slow.

But, if I simply unplug it will my ECU automatically change the timing because it cant see the sensor?

In other word I DO NOT want the ECU to change my timing, whether I am or I am not knocking!

Thanks

Mikelb · #4 11-10-2006, 11:04 PM

ooh... maybe it's phantom knock (bad knock sensor, or it's too tight)... I can wish you the best... I don't know that I would want to disconnect that sensor, b/c I'd rather the ECU pull that timing even if it wasn't real knock, than my motor to blow b/c of knock...

gthompson97 · #5 11-10-2006, 11:05 PM

What are you running that it's knocking? A car shouldn't knock just because. Either you're beating the piss out of it on 87 octane or it's something else, but I doubt you're knocking.

AbsoluteGTR · #6 11-11-2006, 12:22 AM

Quote:

Originally Posted by gthompson97

What are you running that it's knocking? A car shouldn't knock just because. Either you're beating the piss out of it on 87 octane or it's something else, but I doubt you're knocking.

You think? Is it really a rare occurance for knock to occur.

I use 93 octane and the car is set at 15-16 psi. When someone came to test drive the car (I am trying to sell) he said that the car was knocking.

SO, by removing/bypassing the knock sensor I can see if my car has this 'phantom knock'...since I do not have a logger and so on.

Mod wise I am running a downpipe and an open air element plus the MBC set at 15psi. THAT IS IT! What could be the problem? I have dealt with this problem since I bought the car and it is slow as shit.

ANY help or advice is needed.

EDIT> The car does NOT have a CEL.

THANKS!

Thor06 · #7 11-11-2006, 12:44 AM

You should not be bypassing the knock sensor. If you pulling timing, you need to fix the problem, not jimmy rig it to work good for while you are selling it.

AbsoluteGTR · #8 11-11-2006, 12:51 AM

OK. You guys are not understanding why I want to do this.

I do not have a logger.
Therefor, I cannot tell if my car is knocking and that is the reason why it is so slow.
By disconnecting/bypassing the knock sensor I will see if knock is really the problem.
When I unplug it and the car actually pulls hard then I will know that I am knocking.
So at this point in time, I know what the problem is and from there I can fix the problem.

As of right now, I am simply trying to diagnose the problem.

Thats the only reason why I want to do this!

Any one have any suggestions?

Mikelb · #9 11-11-2006, 08:50 AM

Ok, I understand what you're wanting to do. But, if you pull that sensor and do knock, the car won't pull timing and you could blow the motor.

I would suggest checking your timing. One of your cams might have jumped a tooth. That can make a car slow as shit. It's happened to mine.

david-b · #10 11-11-2006, 09:56 AM

Did you do a compression test? Leak test?

AbsoluteGTR · #11 11-11-2006, 10:22 AM

My compression is at 150,160,165,170.

So I am pretty sure my timing is fine, otherwise I would not get these results.

I wont blow my engine for the 5-10 minutes that i unplu the senor and drive it.

Any ideas on how to hardwire it?

Thor06 · #12 11-11-2006, 11:18 AM

Well, I dont know if it could cause it to not pull like it should, but there isnt supposed to be more than a 15psi differential between the different cylinders, you've got one thats 20 below.

gthompson97 · #13 11-11-2006, 12:55 PM

Even with a 20 psi difference in compression, it still wouldn't cause the car to be slow like he's talking. I really think your problem is elsewhere man. There's no physical reason that you COULD be knocking (or should be), which leads me to believe it's something else. How does the car run besides that? Idle fine? No popping or backfiring or anything? Done a boost leak test?

MT-2500 · #14 11-11-2006, 01:23 PM

Quote:

Originally Posted by AbsoluteGTR

Thats the thing, the purpose of me jumping the knock sensor is so my ECU will not change my timing and I want to see, by jumping it, if my car is suffering from knock, because it so incredibly slow.

But, if I simply unplug it will my ECU automatically change the timing because it cant see the sensor?

In other word I DO NOT want the ECU to change my timing, whether I am or I am not knocking!

Thanks

Well that is a good question on what the ECM will do if a knock sensor is unpluged.
Some ECM will go into a backup/different mode if a main sensor is unpluged.

Knock sensors work off of resistance value.
You could wire in a resistor the same as your knock sensor or just get a extra knock sensor and hook it up with it grounded to engine for a test.

But to see what the ecm is doing with timing or if it is picking up a knock you will need a scanner that can read it out.

If the knock sensor is working right and picking up a engine knock or pre ign spark knock it should retard the timing.

AbsoluteGTR · #15 11-11-2006, 10:20 PM

Quote:

Originally Posted by gthompson97

Even with a 20 psi difference in compression, it still wouldn't cause the car to be slow like he's talking. I really think your problem is elsewhere man. There's no physical reason that you COULD be knocking (or should be), which leads me to believe it's something else. How does the car run besides that? Idle fine? No popping or backfiring or anything? Done a boost leak test?

Where else would the problem lie? My idle is fine. Kinda low around 600-700.

The is no popping or backfiring at all. Done a boost leak test. Only leaks are at the throttle body shaft seals. I KNOW that can NOT be the cause of the problem.

For daily driving, the car is fine. But if you needed to get on the car, it will not get up and go. The car doesnt pull hard at all.

At 3K RPM I can feel the turbo kick in, but it just doesnt push me back in my seat.

Quote:

Originally Posted by MT-2500

Well that is a good question on what the ECM will do if a knock sensor is unpluged.
Some ECM will go into a backup/different mode if a main sensor is unpluged.

Knock sensors work off of resistance value.
You could wire in a resistor the same as your knock sensor or just get a extra knock sensor and hook it up with it grounded to engine for a test.

But to see what the ecm is doing with timing or if it is picking up a knock you will need a scanner that can read it out.

If the knock sensor is working right and picking up a engine knock or pre ign spark knock it should retard the timing.

I read on tuners that if the knock sensor is NOT plugged in the ECU will automatically pull the timing. Even if the car is not knocking, the ECU will automatically pull the timing and make the mixture extremely RICH just to be safe.

Come to think of it, my gas mileage is absolutely HORRIBLE.

It seems as though everything I think of points to knock!

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