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5-Series (E12,E28, E34, E39, E60) Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)

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Old 09-19-2011, 08:17 PM   #1 (permalink)
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4 out of 6 clynders are not firing

I am helping my son's friend who has a 95 525-i (m50, I think). It started running very rough. We got the car to start and run with no engine codes showing up.
We started disconnecting the coil wires.
After we removed 1, 2, 3, and # 6. ( all 4 were removed ) there was no difference in how sad the motor ran. It appeared that only cylinders 4, and 5 were actually firing.(Yes it was running with only 2 coil wires conneced)
I got 12 volts at all 6 coil connectors.
The resistance was about .8 to .9 for the cylinders in question.
Number 4 and 5 were about .4 to .5 ohms.
We are planning on swapping number 4 and 5 coils with other cylinders to see if any difference.
Questions:
Forgive me for I am a BMW nubie...
or if we have caused other problems by our uninformed testing procedures...
Any other possible sensor or an engine ecm issue?
Thanks,
Signed,
A frustrated father.
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Old 09-21-2011, 02:19 PM   #2 (permalink)
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Are the coils you removed making a spark?
if they are then your problem is your injectors are not firing properly usually caused by a faulty crankshaft position sensor.
If they are not then you might want to check the Camshaft sensor.
hope this helps.
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Old 09-21-2011, 02:36 PM   #3 (permalink)
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SOunds like a plan on where to start:
I WAS getting a spark when i removed teh coils and used a spare spark plug grounded against the head.
I repalced teh coil wire on # 6 and it is firing, now just the first 3 are not firing. I can remove 1, 2, & 3 coil wires and ther is no difference in how the engine sounds.
I was goign to look at fuel pressure next.
I will look at the crank sensor.
Mike
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Old 09-21-2011, 04:31 PM   #4 (permalink)
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Update:
I checked the Crank Sensor.
..first this is the M50 engine, no dristributor, just 6 coil-on-plugs...
The crank sensor read 530 ohms. I have read whgere the M50 is supposed to be 1280+/- 10%
Am i correct in the Crank Sensor needs to be repalced.
recap... no clynder firing in 1 - 3. I get a spark at the coil.
I can remove all three coil wires (1 to 3) at the same time and no difference in results
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Old 09-21-2011, 10:59 PM   #5 (permalink)
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im pretty sure you're right ill check the manual tomorrow morning and let you know sometime in the afternoon
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Old 09-21-2011, 11:01 PM   #6 (permalink)
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Update # 2.
The info I had on the crank sensor was wrong.
540 should be the correct reading.
So the Crank sensor is good.
Will look at fuel pressure and compresion at each clynder.
I will also try to get some readings from each injector.
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Old 09-22-2011, 05:53 AM   #7 (permalink)
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Welcome to the Werkz.

You could try putting the coil packs from some of the "inquestion" cylinders onto the "good" cylinders to see if the problem is in the coil pack or the cylinder position.

Have any codes shown up in all this moving around?

Is there any rubbish on the inside face of the position sensors?

Was anything done immediately prior to the problem occurring?

Are the "bad cylinder" injectors firing at all? (Listen with the pointy end of a screwdriver on the injector body and the handle in your ear.) A long screwdrive is best.
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Old 09-22-2011, 06:27 PM   #8 (permalink)
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what brettski^ said.
hmmmmmm??? *thinks*
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Old 09-26-2011, 06:28 PM   #9 (permalink)
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Update # 3:
I swapped out the back set of 3 coils for the front set of 3 coils. I found out it does matter if I am running off the back 3 cylinders or the front 3. By removing any 3 coils, it does not matter which 3, it still runs the same.
I hear all 6 injectors "clicking" as well as saw a voltage pulse at all 6 injectors.
I am going to check the fuel pressure and cylinder compression next.
Is there any other ignition sensor or device besides the DME that would cause the same affects?
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Old 09-26-2011, 07:25 PM   #10 (permalink)
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hmmmm......
before anything check this.(BMW E34 Idle problem FIXED! - YouTube just be your problem if not then try getting codes from it...
is the problem only at idle? iac valve could be dirty
check for vacuum leaks, check gaps in spark plugs if they've been recently changed, and check their condition you can tell if the engine is running rich or lean by how the spark plugs look, check if fuel filter is clogged, throttle sensor. ill update later if i remember anything else.
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