BMW E36 Blog

BMW E36 Knock Sensors

24th July 2008

BMW E36 Knock Sensors


Hi all,

As you may know, I’m still having a problem with my car’s idle. I mainly have 2 problems:

1. When I start my car, the idle bounces for a while and then it becomes stable.

2. While driving, I sometimes notice that the RPM (Rotation Per Minute) moves down until it reaches 200 or maybe less then it comes back again especially when I’m pressing the clutch pedal.

After running an extensive research about these problems, I’ve found many solutions or you may call them suggestions and they’re all over the forums. The solutions for a perfect idle in a BMW E36 are:

1. Cleaning ICV (Idle Control Valve): A very straight forward task. This unfortunately didn’t solve my problem completely but it helped a little bit.

2. Checking/Replacing the TPS (Throttle Position Sensor): I tried to replace it, but nothing has changed.

3. Check for vacuum leaks: Just buy a carborator cleaner can and while the engine is running, spray it around the engine and make sure to listen to the engine sound and see if you can detect any change in the engine’s idle. If anything has changed, it means that you have a vacuum leak. This didn’t result in any problems in my case.

4. Check the ignition coils: I didn’t find any problems with this either.

With these options out of my way, I’m left with a knock sensor error code when I check my car for problems. Actually it’s the 2nd knock sensor which is located in the left side of the cylinder block. For those who don’t know what a knock sensor is, it’s a sensor used to monitor the combustion chamber for engine-damaging knock (according the the Bentley Manual). Unfortunately, the second knock sensor requires removing the upper section of the intake manifold to replace it. So, as you can see, it’s not a very straight forward task, so I took the car to a mechanic and he replaced it (I suggest you do the same if you have the same problem). Now, the knock sensor is working properly. I also asked him about the DISA valve and it turned out that I had a vacuum leak that prevented it from working properly.

Now, after I fixed both problems, I got rid of the second problem completely. Now, I need to do more research about the first problem. I know it’s not going to be that simple and I will need to dig deeper before I have my perfect idle. But I’m not going to despair…

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posted in Engine, Technical Info, Tips & Tricks, Uncategorized | 18 Comments

8th July 2008

DISA Valve Inspection


Hi All,

Anyone had a chance to read my previous post BMW E36 M42 DISA Valve and check the DISA valve for me? :p Come on, no one with M42 engine? or are you afraid to discover a problem in your engines?


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posted in Engine, Uncategorized | Comments Off on DISA Valve Inspection

3rd July 2008

BMW E36 M42 DISA Valve


As you may know, I’m facing trouble with my BMW E36 318is idle and until now, I was unable to totally fix the problem. I’ve cleaned the ICV, changed oxygen sensor, checked for vacuum leaks but this didn’t solve my problem. I still have a problem in one of the knock sensors, but mechanics say that it doesn’t affect the idle in anyway. Well, although this may sound correct, but I’m going to change it anyway simply because I hate to have such a problem in my car which may cause some damage to the engine.

Now, I’ve discovered last week that my DISA valve doesn’t close. For those who don’t know what the DISA valve is, please check here and here.

BMW E36 M42 DISA Valve

I’ve tried to reach to the DISA valve and check to see if the actuator arm retracts if I turned my engine on and below 4,700 RPM. I found out that the DISA valve doesn’t close and I think this may affect the idle although I’m not 100% sure of that.

So, what I’m looking for is some help from you guys. Anyone with M42 engine can confirm that the DISA valve actuator arm retracts when you start your engine. To check that simply:

1. Reach with your hand behind the DISA diaphragm.

2. You should feel a small arm that you can press with your finger when the engine is off.

3. Now, according to the Bentely manual, the actuator arm should retract when the engine is started (at idle).

Now, can you feel the actuator arm retracts when the engine is started? Can you please confirm this?

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posted in Engine, Tips & Tricks, Uncategorized | 2 Comments