Engine rough and shake after reached operating temperature.

[lorensiuswlt]

Hi fellow bimmers,

I have problem with my e36 m50 (94). The car started shaking and idling rough (like diesel engine) when the engine reached operating temperature (the temp needle was in the middle of the gauge). It also took a long cranking before start. It didnt happen when i started the car in the morning (after sitting all night in the garage).


https://www.youtube.com/shorts/Wd0vpd2CVx8


Do you guys have idea or suggestions ? Thanks

[Eric93se]

This is usually a vacuum leak so check all your vacuum hoses, intake rubber bellows also the valve cover gasket can have a vacuum leak.

Can also be a bad coil or injector. If you want to get better at doing diagnosis get INPA on a laptop, the software is free on the forum and a cable is like $30.

[lorensiuswlt]

This is usually a vacuum leak so check all your vacuum hoses, intake rubber bellows also the valve cover gasket can have a vacuum leak.

Can also be a bad coil or injector. If you want to get better at doing diagnosis get INPA on a laptop, the software is free on the forum and a cable is like $30.

Hi eric, thank u for your reply.

Here is what inpa read from dme 40.1

Error code 79. Is that a crankshaft or camshaft? or both ?
Error code 68. Sporadic air mass error, not present. I tried to unplug the MAF connector when checking the shake problem. Is that the cause?



Here is the video starting the engine.

https://www.youtube.com/shorts/Wd0vpd2CVx8

Update:

I clear the error codes and start the car again until the engine shakes. Now the Air mass error is gone and but the crankshaft sensor error persists.

[Eric93se]

I would replace the Camshaft sensor. You can test the Crankshaft sensor, on the M50 the crankshaft sensor is just above the engines main crank, the resistance should be close to 510 ohms.

If would be a good idea to smoke test the engine to find any vacuum leaks.

Nice work getting INPA results up so fast.

- - - Updated - - -

Watching the video the rpm holds steady but she runs rough. Did you buy gasoline from a place you don't normally go to?

[lorensiuswlt]

I would replace the Camshaft sensor. You can test the Crankshaft sensor, on the M50 the crankshaft sensor is just above the engines main crank, the resistance should be close to 510 ohms.

If would be a good idea to smoke test the engine to find any vacuum leaks.

Nice work getting INPA results up so fast.

- - - Updated - - -

Watching the video the rpm holds steady but she runs rough. Did you buy gasoline from a place you don't normally go to?

Hi eric, thank you, i'll check the crank position sensor.

I bought the gasolione from the station that i usually buy. I fill up the the tank for about 10 litres after it almost empty the day before the problem occured.

[lorensiuswlt]

Hi guys,

Problem solved by replacing both cam & crankshaft position sensor (both original BMW (siemens with BMW logo)). But i have new problem, the idle rpm seems a bit higher than usual when warm, the rpm needle slightly sits below 1 (1000rpm). And sometimes it take a 1-2 seconds to drop below 1000rpm after rev up. When AC is on, the rpm drops to in the middle of 1 and 0 (maybe arround 500-600rpm). Also seems that it has poor mpg also.
Any ideas on this ?

https://youtube.com/shorts/hktW_5InYww?feature=share


Thank

[Eric93se]

You have the M50 engine? If it idled closer to 600rpm before the repair then I would guess it has a vacuum leak possible due to whoever did the repair. Sometimes its just due to a worn out intake boot (the rubber piece after the mass air sensor) they get cracks and leak air. You can ask if they removed the intake manifold when they did the job, I doubt they did but its possible because then its possible the vacuum leak is from the intake manifold not seating properly.

Anyway, it should get smoke tested for vacuum leaks.

Do you work on the car or do you take it to a mechanic?

[lorensiuswlt]

You have the M50 engine? If it idled closer to 600rpm before the repair then I would guess it has a vacuum leak possible due to whoever did the repair. Sometimes its just due to a worn out intake boot (the rubber piece after the mass air sensor) they get cracks and leak air. You can ask if they removed the intake manifold when they did the job, I doubt they did but its possible because then its possible the vacuum leak is from the intake manifold not seating properly.

Anyway, it should get smoke tested for vacuum leaks.

Do you work on the car or do you take it to a mechanic?

Hi Eric, thanks for the quick reply;

Yes i did it myself . I didnt remove the manifold, just the fan, upper hose (adding coolant & air bleeding after that), solenoid valve and the oil hose to get free space to remove both sensors. Yes i see some cracks on intake boot, the cracks exists before the repair. I guess the cracks only on the outer side.

20221208_182312.jpg

I cleaned the throtle body, maf sensor and tightening the clamps on intake booth this morning, drove the car and no change. I don't have the smoke test tool, but i'm thinking on build my own smoke test , i see some diy on youtube .