e36 bad / no idle - crankshaft sensor??

kani · 08-08-2008, 12:23 AM

93 320i has no idle or a bad idle, gives a code of crankshaft sensor with a 3rd party scan tool for bmw. the previous owner had changed the sensor, it worked for 2 days, then it went bad again and the code came back. he was suspecting the whole wire harness needed replacing.

but whats weird is that shouldnt a broken crankshaft angle sensor cause the engine to not start at all??

is this the wet/bad ecu/dme problem?? I'll check the dme and then probe the wires. I get rpm on the instrument cluster, doesnt it get the rpm info from the crankshaft angle sensor??

does the crankshaft angle sensor have a connector somewhere?? where?? its not at the sensor.

coolbear1 · 08-09-2008, 11:38 PM

The crank sensor plug is under the intake manifold, just above the idle control valve on the M50 engine. I'm not sure what engine is in the 320i, but if it is the M44, I think it is in the same place. If the sensor is on the front of the engine, it has a wire cove that bolts to the water pump. The sensor wire emerges from under the cover between the oil filter and the lifting eye.
The plug is in a support bracket mounted just above and forward of the back of the starter.
The bracket has two plugs in it. The other plug is to the idle valve.

The car could run with a faulty sensor if the ECM was getting at least some signal.
The sensor reads the pully (harmonic ballancer) on the front of the crank shaft. Make sure the sensor and pully teeth are clean. If the Intake maifold is plastic and the head and injector rail are black plastic you have a M50. If you have a lot of metal on top of the engine it most likely is a M44, and this may not apply. Bad idle could be a dirty Idle control valve, a intake leak, or vacuum leak, to name a few.

kani · 08-10-2008, 12:22 PM

Its the M50 engine. I think the connector is somewhere far enough under the intake and the intake should be removed to get to the connector and probe the wires. The problem went away by itself this weekend when I was driving vigurously around the mountain roads, I hope it wont come back

kani · 08-17-2008, 09:33 AM

The problem came back after a week. I popped open the ecu compartment and since it seemed to be dirty etc. opened the ecu too. The lower pcb is heavily oxidized and has a few bad solder joints. Probably all the computer boxes in the car and the instrument cluster also have the same problem(s). Doh. Taking it all apart and cleaning/re soldering piece by piece..

Pics are now offline but can be seen at http://usagi.1g.fi/kuvat/bmw/dme when the server is back online.

How does the dme open completely?? the top board seems to come out by pulling up and then out of the ecu connector, but is there a clip or something somewhere?? Or should I just use more force??

I think all e36 owners should check their DME for corrosion/oxidization/crap in it, before it gets so bad that it cant be fixed anymore. In the early stages cleaning it up will be enough.

coolbear1 · 08-18-2008, 09:04 PM

The ECMs on E36s, are notorious for getting wet from leaking or rusted vent cowlings.
The CP sensor connector is not that hard to find without removing the manifold, when you remove all of the intake components amd the alternator duct. you can actually see it mounted in a metal bracket along with the connector to the idle control valve..

kani · 09-08-2008, 02:16 PM

thanks for the tip coolbear, i was looking at the instruction on this site, that told to remove the intake manifold. but it was easy to get to per your instructions. just remove the air filter box & the alternator duct and you get enough space to get to the connector and clean it properly. i put some electronics cleaner into it and its working.. time will tell if its a permanent fix. the car drives great now

coolbear1 · 02:02 PM

Great.
If it does it again, replacing the sensor is not hard, if you need help, I will try to type you through it.

kani · 09-11-2008, 06:58 AM

The previous owner had changed the sensor. When the car is cold and if it has this problem its easy to grab the connector under the intake manifold and squeeze it shut with your hand then the problem goes away, runs perfect again for a day to a week. so I'm thinking the connector on the wiring is busted internally or something, the vibration and heating up/cooling down makes it go loose again and loose contact. Cleaning the connector didnt last but a few days again. Can you change the connectors on bmw wiring or do you need to get a whole new engine wiring loom??

If the latter is the case Im thinking just cutting the connector off and soldering the cables together. This should get rid of the connection problem in the connector for good

coolbear1 · 09-12-2008, 05:28 PM

I had a similar problem with the sensor on my car. the molded plastic sensor plug had a internal break actually inside the plastic itself.

I did not find it until after I replaced the sensor.

Curiosity made me ohm the sensor out.

The resistance was all over the place.

After I replaced the sensor, I cut the wires on the bad one and ohmed it out again.

It was the plug itself, not the sensor.

If I where contemplating cutting the cars harness, I would cut, and check the sensor, and its plug first.

You would have to cut it anyway, and if you find it to be bad, you could just buy a sensor instead of cutting on the cars wiring.