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Bypassing knock sensor


AbsoluteGTR
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
11-10-2006, 05:52 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.


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
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
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
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
11-11-2006, 12:22 AM
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
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.:nono:

AbsoluteGTR
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
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
11-11-2006, 09:56 AM
Did you do a compression test? Leak test?

AbsoluteGTR
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
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
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
11-11-2006, 01:23 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

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
11-11-2006, 10:20 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?

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.


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!

crunchymilk55
11-12-2006, 12:40 AM
Get a logger. Less than 100 bucks.

Thor06
11-12-2006, 12:51 AM
Shit, but Mike's. Check his ad, I think hes had that bastard for sale since before I spun a bearing.

gthompson97
11-12-2006, 01:53 AM
I understand that you think it's knock because of how it runs, shitty mileage, the guy told you it was, etc, but you really have no real signs that point to knock. Bad turbo maybe? I don't know man.

AbsoluteGTR
11-12-2006, 11:39 AM
Get a logger. Less than 100 bucks.

The logger is a 100 bucks. But what about the software and all the other stf that goes along with it.

Anyways I have a laptop, cant I just use that?

EDIT> As for the bad turbo part, I doubt it. The turbo has absolutely ZERO shaft play and spins freely and everything.

MT-2500
11-12-2006, 12:03 PM
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.






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!

Check the tune up end and run a backpressure test on exhaust system.
Good Luck

AbsoluteGTR
11-12-2006, 01:02 PM
Well I am running just a downpipe so I bet I have no backpressure, lol. Just to put it out there, my exhaust rattle...cant that make the knock sensor give off a false rading?

gthompson97
11-12-2006, 03:23 PM
Check the tune up end and run a backpressure test on exhaust system.

What in the hell good would that serve?

Well I am running just a downpipe so I bet I have no backpressure, lol. Just to put it out there, my exhaust rattle...cant that make the knock sensor give off a false rading?

It might if it's banging around loud enough? Any why are you running just a downpipe? It shouldn't be a problem being as turbo cars don't rely on as much exhaust velocity (also known as the incorrect term of "backpressure"), as NA cars do. Backpressure is bad in any car, it fights exhaust velocity, therefore slowing down exhaust flow and causing a loss in power (and overall efficiency).

AbsoluteGTR
11-12-2006, 06:27 PM
It might if it's banging around loud enough? Any why are you running just a downpipe? It shouldn't be a problem being as turbo cars don't rely on much exhaust velocity (also known as the incorrect term of "backpressure").

I know, lol. I read all of kjewers post on that!

I wish I wasnt runnin just a downpipe (it really coming off where the center console is) but the previous idiot cut it off....:disappoin

Any more suggestions?

MT-2500
11-12-2006, 07:45 PM
What in the hell good would that serve?



It might if it's banging around loud enough? Any why are you running just a downpipe? It shouldn't be a problem being as turbo cars don't rely on much exhaust velocity (also known as the incorrect term of "backpressure").



Quote:
Originally Posted by MT-2500
Check the tune up end and run a backpressure test on exhaust system.

What in the hell good would that serve?


Well I am from the old school.:grinyes: :shakehead :lol:
If it is not running good they always told me to tune it up.
Works for me. :rofl:

AbsoluteGTR
11-12-2006, 08:39 PM
It shouldn't be a problem being as turbo cars don't rely on much exhaust velocity (also known as the incorrect term of "backpressure").

The way I understood it when I read kjewer's post was that infact that turbo cars DO rely on exhaust velocity and NOT exhaust backpressure. Its just that people assume backpressure and velocity and the same!

gthompson97
11-12-2006, 08:59 PM
Whoa typo! That is NOT what I meant to say. You are correct. Backpressure in ANY car is bad, it's what slows down exhaust velocity. Exhaust velocity is good in any car, but more in NA than turbo cars. That's what I meant to say, it's not AS important in turbo cars as NA because the NA relies solely on the complete flow through the whole system, it doesn't have the turbo to help with intake. NA's need ALL the flow they can get through the whole cycle to run efficiently and have any power what so ever.

I edited my post just so I don't confuse the shit out of anyone. :)

AbsoluteGTR
11-12-2006, 10:25 PM
I edited my post just so I don't confuse the shit out of anyone. :)

Great, now people are gonna think I'm on crack, since I quoted you on somethig you never really said.... :evillol:

Anyways, I am gonna check out the talon tomorrow and see if there is any blackish color goo on the back of the knock sensor (which idicates it is bad and has melted). Im gonna make sure that the guy who rebuilt the engine didnt torque the hell out of it, because then it will pick up anything that knocks/rattles and it will tell the ECU that the car is knocking when in fact it really could not be... (In other words by overtightning it you make it too sensetive)

The correct torque value of the knock sensor is 17 ft/lbs...just for future searchers! Just hand tighten it and then a slight turn with a 24mm wrench

I just hope that this is my problem, lol.....

crunchymilk55
11-13-2006, 10:31 PM
the turbo is the source of all the backpressure that is needed.

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