520i knock sensor

[deepblueE34]

good morning gentlemen,really need some advice from the resident E34 gurus. In a recent visit to my mech. to investigate my high fuel consumption, and after plugging his scanner to my 520i he said you need to change two knock sensors. I didn't realize the magnitude of his revelation until I called the "stockist" at jalan ipoh to inquire about the price of these cute little devices. Of course, after being told that it will cost me RM600 a piece, I decided to see if I can find them cheaper online. Which brings me here. Now I found two parts that look exactly the same to the naked eye, one for 520i and the other for 525i. the part numbers are 12141730029 and 12141738667 respectively. The 520i part costs almost twice as much (maybe due to rarity of 520i e34's) . Which puts me in a dilemma, whether to go for the exact part and pay more or pay less and risk the part not fitting. What should I do?Appreciate your help :top:

 

[deepblueE34]

Apparently, the 520i version is compatible with the Siemens ecu (different connectors) and the other one with the Bosch ecu.

btw, I'm looking for a scanning tool for my E34. Any one interested to sell or lease one? please give me a shout. Also, if any one is kind enough to point me to a reliable/cheap one that I can get online I'll be grateful.

Thanks!

 

[pussy]

why do you need to replace the 2 sensors ? both died at the same time ? can't be so...

the knock sensors on all bmw engines lasts for a life time, no problems on it.



do you know the function of the knock sensor ? it's supposed to sense the ping-ing of the engine due to faulty air-mass, bad petrol, mis-firing injectors, spark plugs, carbon built up in engine pistons.... it sensor the ping(knock) and sends signal to the ecu to either advance or retard the ignition timing...
if the it reads 'knock-sensor' fault, it could mean other factors causing it. check those i have listed...plus the fuel regulators, on the 520i, they knock out early due to age.

 

[deepblueE34]

Thanks pussy for your advice.

Yeah, I read a bit about the function of a knock sensor. Like you pointed out, both sensors going out at once is a bit suspicious. Maybe my mechanic is taking me for a ride (no pun intended). Next week will try to consult another one. So far, my understanding has been that a fault code indicates that the component is not functioning properly. Since, in this case, a working knock sensor will alert the ecu of knocking due to other components' abnormal operation (MAF sensor, injectors, etc.) and shouldn't be throwing a fault code.

Hopefully, will find the culprit for my high FC without spending too much. Will keep you updated.

 

[deepblueE34]

Hello gentlemen,

OK, so I thought I'd do another diagnostic run before replacing knock sensors, which showed no fault codes at all, from knock sensors or otherwise, which is good of course. Nevertheless, I'm puzzled by the high fuel consumption.

What I'd really like to know if my current FC is normal for a 520i with 4-speed GB, or as i feel way too high. Am getting at best 15.2 L/100km mixed driving and about 10.5 L/100km pure highway @ 100-120 km/h. I drive as light footed as humanly possible. before this I drove an audi A6 C4 2.0L (4 cylinder, 8 valve) for a year and it never went higher than 13L/100 city. Shouldn't an e34 fair better?

Also for those with this same engine and a jatco gb, how is your FC like? I'm considering tossing my GM gb for a jatco if it helps the FC. How about that?

Please fellow E34'ers HELP!