Knock Sensor By-pass

[ryanmaynard]

I have a 95 325i with CAI, Dinan chip, light weight flywheel, M3 clutch, yada yada yada, but its running extremely rich due to issues with the knock sensors. The flywheel has some chatter that I believe is triggering the knock sensors to retard the timing. I was wondering if anybody would be so nice as to give me tips on by-passing these sensors, what ohm resistor I should use, etc.

Thank you in advance

[Tefal]

Autodata states 1M ohm resistance

[nidecker]

anyone tried?

I would like to test that before removing my intake manifold...

I tried to connect an other knock sensor directly to the harness near the ECU... but the car was running worst... (probably because there was no vibrations....)

I would like to test something else, maybe a the resistor...so 1M ? I'm all set to test but a little bit affraid of putting a resistor...

give me news please
thanks

[nidecker]

I changed the easy one (cyl. 1-2-3) knock sensor...

Do you think it will work if I wire the same knock sensor to the cyl.4-5-6 wires ?

thanks for your suggestion.
Pat

[dswads34]

Interesting, let me know how that works out for you please. My knock sensors are due to be replaced (1 is cracked all the way through the side :eek:) and at $55-60/each I would much rather go with a simple bypass like this to avoid spending as much money on repairing them now and in the future as well.

[nidecker]

I wired the 2 ECU knock sensor wire to only 1 sensor (1-2-3)..

everything was running normally... maybe a good test to see if your 4-5-6 knock is bad before changing it..

in my case.. I'm searching for the hesitation problem and it's not the knock.. still have the hesitation.

[Tefal]

If you pick up a problem on a cylinder(let's say #5) that introduces knock(pre detonation e.t.c) and it's on a cylinder where you've ghettoed the knock sensor so it reads just the front 3 cylinders(1,2,3) then you run risk of damaging the engine, i.e burn a hole in the piston e.t.c as the timing won't get retarded to eliminate the problem.

[Herb]

I'm searching for the hesitation problem and it's not the knock.. still have the hesitation.

Have you tried the cam positioning sensor, that was the cause on my 328i.

[328iJunkie]

You guys know theses sensors are kind of important right? Like what if you get some bad gas, it starts knocking and doesnt retard timing... Boom.

[Blanco]

You guys know theses sensors are kind of important right? Like what if you get some bad gas, it starts knocking and doesnt retard timing... Boom.

Dude, no doubt. You guys are stepping over dollars to save dimes. If you can't afford a $50 knock sensor, what are you going to do when your engine blows up?

[Stück]

You guys know theses sensors are kind of important right? Like what if you get some bad gas, it starts knocking and doesnt retard timing... Boom.Pfft.. thats not important. Why fix something right when you can cut and twist some wires together with a resistor electrical taped in there?

[ublemaschine]

Pfft.. thats not important. Why fix something right when you can cut and twist some wires together with a resistor electrical taped in there?
:buttrockThis sound's like a great idea. I'm gonna go do the knock sensor delete mod, fill up on 87 octane, and go do some donuts.



My recommendation would be to fix what is causing the car to run rich and not disconnect your knock sensors.

[nidecker]

I know it can be dangerous...I did that only to diagnose...

It's winter right now here... less chance of knocking.. also.. it's easy to hear if a engine is knocking and I do not hear it .

ublemaschine, I like your recommendations but ..tell me what is the problem?

"My recommendation would be to fix what is causing the car to run rich and not disconnect your knock sensors. "

again here is what I changed :

new o2 sensor
new fuel filter
new vanos seal
new coolant temp sensor
new air filter
new coils and boots
new spark plugs oem

also my ECU is throwing code 1215 if I unplug (alone) the IAT and if I unplug the o2 sensor (alone).. I wanted to test my car in closed loop and code 1215 has been throwed really weird

.....


Have you tried the cam positioning sensor, that was the cause on my 328i.

maybe I should... tired to spend money everywhere.

[mpwr ren rebel]

Don't bypass. Spend the money and fix it right. If it still doesn't fix it, then you need to do some deep investigation.

How are your injectors? Fuel pressure regulator? Think about all the other components associated with it. Any bad fuel lines? etc.

[Blanco]

If you're getting a 1215, use some MAF cleaner on your MAF. Always start with the most obvious solution because throwing parts (and money) at a problem is the worst way to fix it.

You can hear knock at idle, not while the RPMs are past a certain point. Peak torque is when cylinder pressures are their greatest and with the engine running around 4000rpm you aren't going to hear knocking or pinging. That's why the knock sensors are there. If your engine's knocking away at 5000rpm for even a few seconds it's literally doing thousands of miles worth of damage to your bearings, piston rings, and cylinder walls. You may be fortunate enough to never suffer a catastrophic failure or your engine might blow up on the way to work tomorrow. A new knock sensor will cost you less than $100 but a new engine will cost you more than $700 plus a significant investment in time. Don't step over dollars to save dimes.

[nidecker]

Thanks for your care, I replug the knock sensor properly last week... I tried to clean my MAF about 1 month ago with alcool... no improvement at all and the MAF wasn't dirty...

The problem is that I'm getting code 1215... when I unplug an other sensor than the MAF like the o2 sensor and the IAT sensor.. There is something wrong there...

I remember in summer, I was hearing my car knocking (with everything properly wired)... but again.. no code...

...


If you're getting a 1215, use some MAF cleaner on your MAF. Always start with the most obvious solution because throwing parts (and money) at a problem is the worst way to fix it.

You can hear knock at idle, not while the RPMs are past a certain point. Peak torque is when cylinder pressures are their greatest and with the engine running around 4000rpm you aren't going to hear knocking or pinging. That's why the knock sensors are there. If your engine's knocking away at 5000rpm for even a few seconds it's literally doing thousands of miles worth of damage to your bearings, piston rings, and cylinder walls. You may be fortunate enough to never suffer a catastrophic failure or your engine might blow up on the way to work tomorrow. A new knock sensor will cost you less than $100 but a new engine will cost you more than $700 plus a significant investment in time. Don't step over dollars to save dimes.

[ublemaschine]

ublemaschine, I like your recommendations but ..tell me what is the problem?


What exactly is wrong with the performance of the car? Is it running very rich with black smoke? Is it just getting poor gas mileage? Is it misfiring? Is it hesitating at a certain load?

Knocking is a side effect of timing that is too advanced or a lean mixture usually. Running rich prevents knocking, thats why factory turbo cars run so rich under boost. If the car is knocking it is probably running too lean.

How does the car Idle? How is it a part load cruise? How is it under heavy load? With the fault you stated, a MAF issue could be the cause.

[nidecker]

What exactly is wrong with the performance of the car? Is it running very rich with black smoke? Is it just getting poor gas mileage? Is it misfiring? Is it hesitating at a certain load?

Knocking is a side effect of timing that is too advanced or a lean mixture usually. Running rich prevents knocking, thats why factory turbo cars run so rich under boost. If the car is knocking it is probably running too lean.

How does the car Idle? How is it a part load cruise? How is it under heavy load? With the fault you stated, a MAF issue could be the cause.

- Idle perfect...
- Poor gas mileage 20mpg...
- Hesitation at aroud 2-3000rpm ... hesitation reaction also when flooring gas pedal ...
- good on high way or high rpm ...
- With all plugged, i have no code 1444... but with O2 or IAT unplugged = 1215

Is the gas mileage calculated electronically?

tks for helping...

[ublemaschine]

Do you have any codes or CEL with everything plugged in? I really wouldn't be concerned too much with the 1215 code if it isn't there when the car is in its normal running state. Unplugging stuff can cause all sorts of screwed up faults.

Good idle pretty much eliminates vacuum/un-metered air issues. Is the 20mpg city and is the car 5 speed or auto? 20 city with an auto isn't too horrible. I would check the fuel pressure and make sure it doesn't drop off (you can get a fuel pressure gauge for pretty cheap at some parts place).

As far as fuel economy calculation goes, the value displayed in the OBC (if you have the 18 button trip computer one) is calculated electronically and is roughly accurate. I always go by what I calculate from the trip odometer and how much gas I put in when I fill up. My 328 5 spd is about 23/29 combined/highway

[Blanco]

Have you tried some fuel system/injector cleaner? You might have a dirty/clogged/stuck injector or two.

[nidecker]

Have you tried some fuel system/injector cleaner? You might have a dirty/clogged/stuck injector or two.

Yep I tried.. nothing.. tks for helping

[nidecker]

used working MAF and CAM position sensor on the way...

I will let you know..

[nidecker]

news with the new maf...

on the first test drive, i seemed to have been solve but after a couple of days... the hesitation is back...

not easy to solve...

things i tried.. :

- maf sensor
- rebuilt vanos
- coolant sensor
- coils
- spark plugs
- o2 sensor
- injector cleanor

a sign? I have a small idle problem sometimes.. it goes little bit to down and then restablish immediatly...

other thing... it's -25 degrees celsius today and the car run so well :)

thanks for your help.
Pat

[JoeDellio]

Ever figure this problem out?