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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #26  
Old 05-31-2011, 06:32 PM
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Thanks guys, you are too kind

I figured instead of getting new sensors that are at least $70 a piece and will fail the same exact way, just rebuild my original ones. The insulation I used is silicon coated fiberglass rated up to 200C so should be plenty. It seems it doesn't actually take long for the original BOSCH insulation to fail. I replaced my intake camshaft position sensor a year ago and now noticed that the cable became very stiff already...
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  #27  
Old 01-22-2013, 04:57 AM
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There's a quest for a method of testing the BMW E39 knock sensors over here today:
- > E39 (1997 - 2003) > knock sensor ohms
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See also: E39 Bestlinks & How to easily find what you need
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  #28  
Old 01-24-2013, 05:48 AM
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Cross referencing to this knock sensor thread today:
-> E39 (1997 - 2003) > missing knock sensor
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  #29  
Old 01-24-2013, 05:53 AM
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For reference, here's a thread that shows pictures of the knock sensor in situ:
> E39 (1997 - 2003) > kNOCK SENSOR 1



EDIT: Since this thread is the canonical one in the bestlinks, here's a set of related E39 knock sensor threads:
etc.
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Last edited by bluebee; 01-24-2013 at 06:04 AM.
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  #30  
Old 11-18-2013, 10:46 PM
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An important question was asked today in this thread:
> E39 (1997 - 2003) > Is there any way to tell whether the piezoelectric knock sensors are activating?

Quote:
It may be impossible to determine, but, I ask because it would be very useful if we could determine whether the piezoelectric knock sensors have activated in, say, the last FTP.

Is there any register that holds a value that we could read after the fact which would tell us whether the knock sensors have been activating?

If not, can we read an indirect value that implies the same thing?

(For example, how would we determine if the timing had been automatically retarded in the past FTP, due to signals from the knock sensors combined with other factors?)
See also:
- How long does it take a piezoelectric knock sensor to adjust the fuel trim based on the gasoline AKI octane rating of the fuel used (1) & how to better understand the piezoelectric knock sensor operation (1)
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Last edited by bluebee; 06-26-2014 at 10:06 AM.
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  #31  
Old 06-26-2014, 10:07 AM
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There's an attempt at describing how to "see" what the knock sensors are doing to timing over here in this E46 thread today ...
> E46 (1999 - 2006) > Gas saving chips

Quote:
Originally Posted by crowz View Post
Umm actually I KNOW what its doing. You can to.

Take your obd scan tool and hook it up and get a live data connection.

Now go to the section in the live list showing timing.

Now go for a drive. Its easier if someone else is actually "driving" and your in the passenger seat monitoring it.

Get them to accelerate. Watch the timing. You will see it climb very fast then hit a wall so to speak. It will jump around a tad bit there. Your seeing the computer react to the knock sensor.

The part you need to change in thinking on this is that the timing never climbs much and will only hit the knock point under heavy loads. When in reality the advance point to cause knocking is hit most of the time at fairly low load amounts. Heres how it worked in the old days so maybe it will make more sense.

In the old days you set a base time when you first set the timing on a motor.

This may be 8 degrees or such on a toyota 18r motor for instance.

Now with that setting its fairly generic and usually wont cause pinging. Remember no computer here. Were talking pure hearable spark knock climbing hills and such. Sounds like the motors knocking real lightly.

Now this setting while ok doesnt doesnt cut it for a correct timing setting. What your interested in is actually TOTAL timing advance. To achieve this you measure timing at 2k rpm's on this particular motor. This reading will show you max advance. What your after is max advance without spark knock. Even doing the timing properly as mentioned you still have a good chance of the driver experiencing spark knock no matter what you do during the total timing adjustment. Since temperature etc can vary. But the goal is to get as much advance out of the motor as is possible while being driveable aka no spark knock. So 90% of the time you still had to pull a few degrees from the final adjustment.

Computerized cars have knock sensors. This allows the computer to adjust the timing very rapidly to hide the spark knock from you. The computers base timing is far higher than you would ever dream of trying on a carb motor.

The designers KNOW its going to spark knock but they dont care since they have it factored into the programming to go to max and back off. It remembers this number and works with it from there. Theres a table that stores these values on most cars programs.

The main point is no matter who you are or how you drive you WILL hit the knock sensor kicking in point everyime you drive you car. How often and how much of course depends on how hard you drive it and the weather in you location.

In modern cars octane raises mpg up till the point you reach what is required to keep it under the knock threshold.

Now the requried octane varies a bunch and how much octane also depends on what your using for base fuel too aka ethanol additives and such.

On my bmw I see a 7 mpg average change between 87 octane and 93 octane over a tank. But we have high temperatures with high humidity and its all hills here.
Quote:
Originally Posted by crowz View Post
Oh also if you want to really see whats happening get auto enginuity. It records all this data as you drive and you can play it back and watch everything and graph everything to see this in action.
Quote:
Originally Posted by crowz View Post
Few more things to throw into this to cover the octane stuff.

When someone asks what is the lowest octane I can run in my car people tell them to read the manual or look for a sticker showing minimum octane required. This of course answers their question and all but did you ever wonder WHY its there and why it requires x octane?

As I posted above the manufacturer runs a much higher base timing with the computer controlled cars. This requires them to make an assumption of minimum octane. If for instance you tune a car to require 91 octane fuel and then put 87 octane fuel in it the car will spark knock. The reason is the base timing is so high that the computer cant compensate for it. It cant pull enough timing to make up for the lower octane fuel. So thats the real reason for minimum octane requirements. The numbers are not there to tell you to run x octane fuel to get the best performance. They are there to tell you to run x octane fuel to avoid damaging the motor.

Yes the car will perform worse going under the recommended octane but the chance of motor damage is really the reason its there.

When doing custom tunes for my LT1 motor in my formula firebird I get my table numbers from doing live data captures which shows spark retarding in the graph it records. Its pretty wild how different fuels effect it.
See also:
- How long does it take a piezoelectric knock sensor to adjust the fuel trim based on the gasoline AKI octane rating of the fuel used (1) & how to better understand the piezoelectric knock sensor operation (1)
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  #32  
Old 06-26-2014, 02:52 PM
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i was told One tank of fuel...

Ive noticed that to be correct...
(looking at the trim data from tank to tank)
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  #33  
Old 08-24-2014, 10:40 PM
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This thread, opened today, is relevant:
> E39 (1997 - 2003) > Engine Knock - Anything specific to the E39 I should know about?


Quote:
Originally Posted by Dolan View Post
Searched the 'Very best' thread and the E39 forum for 'engine knock' and 'pinging' but didn't find much... Hope it's not because of my lousy search skills.

My '03 530i (108k mi) has been pinging under load, usually only noticeable on an incline. I understand what usually contributes to engine knock, but I thought I'd ask if there are any issues specific to the E39 or BMWs in general (because I'm a BMW newb,) which would help in diagnosing it.

There are no codes and the car runs fine. Performance seems to be good too (again - not familiar with the E39 so it might be down on power and I don't know it,) however when climbing a hill at part to mid-throttle I notice a faint pinging sound as I pass parked cars or fences which reflect the sound not audible in the cabin. This happens in mild weather - mid 70's - so not in unusually hot conditions. It's on the second or third tank of 93 octane since I bought it in mid-July and one of those fillups included some injector cleaner. Engine temps are always normal and I'm usually alone in the car, no passengers.

Anything specific to inspect before I start diagnosing a typical lean condition? I'm hoping someone will jump in with "oh, yeah this is very common - it's probably a bad knock sensor."
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