Sporadic Knock sensor errors (channel/bank 2) and 2000+ knock reading cyl 4,5,6 testo

[klaas]

Hi,

Ive messed around with testo so I can use it on my 325i.

Ive read out the values STATUS_K_MW_X_WERT for all 6 cylinders.

When idling the readings are all the time around:

cyl1: 24
cyl2: 26
cyl3: 23
cyl4: 2079
cyl5: 2085
cyl6: 2071

I believe these are the same values are 'Engine roughness' in INPA, however, this is not available in INPA for DME 3.3.1

Also im getting now and then errors in the ECU error memory, but they are rare (1 time in +- 1000km)

These are:

Knock sensor Channel 2
Engine speed 4320
Coolant temp: 91,50

Open circuit
Invalid working area
etc....


Because cyl 4,5,6 knock values are so in high idle and almost the same value...and that they share the same sensor..and there is sometimes an error on this exact sensor..
.... it seems this sensor is broken right?

Also in the hills with the trunk full of bags the engine starts pinging only under 3000rpm... except when i use 102 octane fuel.

Somebody experienced this before? Am i right to conclude the bank 2 sensor is broken?


thanks!

[Eric93se]

Replace the knock sensor, they are known to go bad on the early e36's. If your precat oxygen sensor is old replace that too.

[klaas]

Replace the knock sensor, they are known to go bad on the early e36's. If your precat oxygen sensor is old replace that too.

Does a 1994 E36 count as an early e36 ? its kind of right in the middle

[Eric93se]

By early I mean m50, later M52.

[mowgli520i]

I also checked my knock sensor values with Testo and just as OP, I get the same values. I was concerned to see values ~100x higher on cyl 4,5,6 than on 1,2,3. So I swapped the two sensors: same result. I proceeded to swap injectors, coils and plug between "banks" and I got the same result. I even bought a new knock sensor before all this for bank 2 (cyl 4,5,6) and I got the same values.
But most interesting was 2 days ago, when I disconnected both knock sensors and I was baffled to see Testo not only showing the same values, but they were dynamic values, so they were refreshing just as if sensors were connected, despite Testo throwing a code for both Knock sensors missing. So make what you will out of this, but I don't trust my diag data. Which mean, I'm screwed and I can continue to trow $$$ at the car, trying to fix the issue.

[klaas]

I also checked my knock sensor values with Testo and just as OP, I get the same values. I was concerned to see values ~100x higher on cyl 4,5,6 than on 1,2,3. So I swapped the two sensors: same result. I proceeded to swap injectors, coils and plug between "banks" and I got the same result. I even bought a new knock sensor before all this for bank 2 (cyl 4,5,6) and I got the same values.
But most interesting was 2 days ago, when I disconnected both knock sensors and I was baffled to see Testo not only showing the same values, but they were dynamic values, so they were refreshing just as if sensors were connected, despite Testo throwing a code for both Knock sensors missing. So make what you will out of this, but I don't trust my diag data. Which mean, I'm screwed and I can continue to trow $$$ at the car, trying to fix the issue.

Wij are you screwed, is the engine not running right?

[mowgli520i]

No, it's not. Occasionally when accelerating from light engine load, 1500-2000rpm up to 4000rpm the engine bogs down as if fuel doesn't reach it. Also power isn't where it should be overall, yet, sometimes it runs fine. Fuel consumption increased by 0.5 - 1l / 100kmh. I am experiencing this for 2 years now and it started when 1 knock sensor failed and it also threw a lambda code. Sensor was replaced immediately and both codes cleared, yet symptoms remained. Usually the issue is more noticeable when engine is started, whether cold or hot from previous run and sat for a while. I replaced the following:

Vacuum lines with OEM.
MAF with Bosch
Fuel pump with Pierburg
ECU swap
Injectors refurbished
Head is rebuilt
Exhaust has no leaks pre O2 sensor
Knock sensors replaced with Bosch
Fuel pressure regulator replaced with Pierburg
Cam and crank sensors replaced with Bosch
ICV valve replaced with Bosch
Temp sensor replaced with Bosch
Coils were swapped with loaned Bremis
New NGK OEM plugs
Injectors loaned for a week to test
All engine gaskets are new
Oil changes every 7000-10000km
Throttle position sensor swapped temporarily with a used one
Checked exhaust for blockages and measured temps on the cat. All looks fine
Oxygen sensor changed twice with NGK OEM unit

Once after the first O2 sensor change, the car ran great. Fuel consumption better than ever. I crossed Bavaria's autobahns at regular 170-180kmh speeds, tapping out at 225kmh and frequently exceeded 200km/h and I still used 9.1l of fuel every 100km. I can pull these numbers now if I drive constantly at 120kmh like a granny. This joy lasted for about 3-6 months, then it went back to "normal". Changing O2 sensor once more didn't seem to improve the situation this time. So I'm finally lost.

[klaas]

Well, it seems like the 02 sensor en the knock sensor were never the problem. And that it was a coincidence that the car ran good again.

I dont see fuel filter in your list , has that been replaced? Maybe your loosing fuel pressure after sitting for a while

[mowgli520i]

All filters are new OEM. Pressure was measured and is in spec. Although I did it while at idle. I want to test it while running, but haven't figured out a way yet, other than running long hoses from the rail inlet up to the windshield.

[spyderg0d]

If it was lile that for 6 months, those were the problems.. Now, either you got a cheaper 02 sensor that is now failing prematurely, or you have a new problem. Train rolling problems often happen on old cars that lacked maintenence for a long period of time. Ive had many cars that as soon as you fix 1 thing, 2 more pop up in a seemingly endless cycles.. Such is the life of owning a 25+yr old car at times.

[mowgli520i]

I don't understand what you mean by this part: "If it was lile that for 6 months, those were the problems..". The car was maintained quite well, certainly better than most cars. Everything was replaced. I have it for 6 years and take incredible care of it. It was a 520i, then swapped the engine from 525i donor car. I had to redo the head but it ran great for half a year. The donor car had 200.000 original km on it, owned by one family all it's life and it had a whole folder with dealer invoices going back to not long ago actually. Compression is in factory spec as well. Regarding the O2, both were NGK which is the OEM manufacturer for this car at a cost of $120. I wouldn't mind fixing things, as long as I could fix them. But for 2 years I'm chasing this one problem with no result.

[Eric93se]

Run fuel injector cleaner for the next 3 tanks of gas. Buy a different brand for each tank. I know you've replaced a lot but you can't rule out cat getting clogged by just using a thermal probe, the cleaner should help.