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  #1  
Old 31-12-2016, 07:31 AM
Michael. Michael. is offline
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Default Ignition coil intermittent power

My car has had an issue where it would cut out randomly and then start again for me after I tried again. Sometimes straight away, others after a few minutes. Last week though the car wouldn't start at all. A garage diagnosed that the coil wasn't getting power. When it was given a perm live from the battery the engine ran fine again.

I drove the car home with a temporary cable giving power to the coil this way.

I went out last night to see if I could get to the bottom of it and now the car is running grand again without the temp fix in place so looks like an intermittent issue.

Any ideas where to start on this one?

Cheers
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  #2  
Old 31-12-2016, 02:39 PM
Sceptre Sceptre is offline
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Installing a cut-off switch in the green wire from the ignition to the coil was a useful and very effective way of immobilising the car while giving the impression that it was attempting to start. It may be that you could have a bad connection along this wire or a faulty ignition switch. The coil gets its ground from the Ecu and the positive from this green wire.
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Old 31-12-2016, 02:50 PM
Michael. Michael. is offline
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Quote:
Originally Posted by Sceptre View Post
Installing a cut-off switch in the green wire from the ignition to the coil was a useful and very effective way of immobilising the car while giving the impression that it was attempting to start. It may be that you could have a bad connection along this wire or a faulty ignition switch. The coil gets its ground from the Ecu and the positive from this green wire.

Thank you for this. There is a cut off in my car so I'll start looking around here and that green wire.
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Old 31-12-2016, 07:26 PM
JPK JPK is offline
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Check the crank position sensor if the car has one, usually they will work fine for a little while but as they heat up they begin to short internally and stop working. The CPS controls the ignition coil.
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  #5  
Old 31-12-2016, 07:30 PM
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xworks xworks is offline
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Does the car have an On Board Computer?
The crankshaft position sensor's well being has no effect
on the coil postive at all.
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  #6  
Old 01-01-2017, 12:23 AM
1mochi 1mochi is offline
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Been having the same issue with my 1988 325is having intermittent stalls. Replaced all the relays, including the OBC relay, ignition coil, fuel filter, ignition switch, CPS, TPS, fuel purge valve and AFM (refurbished by Bavarian Restoration); repaired C191 connector - wires were corroded through. All of the electrical/mechanical parts were original with over 295k miles on it so thought one of them had to be the gremlin.

Been having this problem for the past 3-4 years and it was progressively getting worse over time. It started with only in very hot weather (over 102) to just recently every 20 minutes or so.

Car still stalled and finally decided to have an experienced BMW tech takeover. I was worried it would stall on the bridge or highway without a shoulder or pullout so had it towed to my talented BMW mechanic. Good thing I have a 200 mile tow plan on my AAA card since he is located 120 miles from home.

He found it being the wiring in the harness. His plan is to try repairing it, but may need it replace it; he indicated it is where the wires are shielded from interference.

I recommend doing the cheap and easy fixes first; the fuel and main relays, and checking the C191 connectors for corrosion.

Good luck.
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  #7  
Old 01-01-2017, 12:13 PM
Michael. Michael. is offline
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Thanks for this,

The car was working fine again yesterday which didn't help as I can't find the problem when it is not there for me. Went out this morning to head to work and the ignition coil isn't getting power again, so I had to take power direct from the battery again to it to get on the road.

The digging will continue when I get time. It's a pain in the hole
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  #8  
Old 01-01-2017, 02:15 PM
george/glanmire george/glanmire is offline
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If you have an alarm installed or there is an old one installed
rip it out but remember where all the wires were taken from,
i had a touring before and it nearly broke me with that issue,park
up to go into the shop,back out to start it,no joy,wait ten minutes no
problem off i go again,take pictures before you disconnect
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