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Discussion Starter · #1 ·
a couple of days ago i had a thread regarding Coil meltdown and the car only running at 4 cyl, i bought 2 new coils and replaced them. the car now runned Smooooth for 2 hours(without any surging or hessitating on part throttle) Then is startet to Surge again, and went back to old condition the day after.

Yesterday i changed all the Sparkplug sockets between the coil and plug. The car got a bit better, and is now great when its cold, but starts surge when it gets half warm\warm.

I've read earlier about ppl that have expirienced old coils failing after replacing with new coils. Could that be the case since the car worked fine for a while after coilchange? But why is the car good when its cold?

The O2 sensor is new, new sparkplugs, new airfilter.
 

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Hello, I think you should be looking at the fuell pump. Have you notice a strong smell of petrol from the car ? were the plugs wet when you pulled them out ?
My car had similar problem to your's and changing the fuel pump fixed it.
Cheers.
 

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Discussion Starter · #3 ·
Hmmm, No havent smelled any strong petrol smell from the car, except when it didnt run on all cyl because of the coil. They wont wet either when i checked last time :)

When i drive it feels like its misfires on one cyl or something, its kinda anoying!
 

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Crzy, I think the best thing is to get the car on BMW diagnostic and see if it can pin point the fault for you. You could end up spending a lot on various parts chasing this problem.
 

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Hmmm, No havent smelled any strong petrol smell from the car, except when it didnt run on all cyl because of the coil. They wont wet either when i checked last time :)

When i drive it feels like its misfires on one cyl or something, its kinda anoying!
Make sure there is no water in the plug holes. I had the same symptoms with just a little water in number 1 plug socket
 

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Discussion Starter · #6 ·
I've had the car at ha diag. And didnt find any other fault than the failing abs sensor.

Thats the problem!

I think i'll change all the coils since its was good after the last change. and 4 of them are old.

I cant see any oil or water in the plug socket :\
 

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Maybe you should check water temp sensor.It is known that the wires to this part (near exhaust manifold) can become brittle and need cut out and replaced.
 

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Discussion Starter · #9 ·
I checked that yesterday, if its the blue one :)

The wires looked fine, but didnt open the isolator to check inside? but it wasnt brittle
 

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I checked that yesterday, if its the blue one :)

The wires looked fine, but didnt open the isolator to check inside? but it wasnt brittle
If you hook the car up to a diagnostic system it will tell you the coolant temperature while running (Not Carsoft). I replaced my coolant temp sensor with the correct one with gold plated terminals.
 

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Discussion Starter · #11 · (Edited)
Aha! Yes when i had the car at diagnose the coolant temp came up, so that shouldtn be the problem then! :)

I just took out the spark plugs to see. What can we read from these?

1-2 cyl

3-4

5-6
 

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Discussion Starter · #12 ·
The new coils i got from a local dealer was Beru coils with number 0040100014, when i google them i dont get the M5 listed.

Are the new coils wrong? whats the difference in case? i see they are compatible with E31 840CI and 740i.
 

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No2 looks a bit sooty, imo.
Coil prt no from realoem.com - 12131730766

Have you cheked your resistors in the dme as suggested in the other thread ??
 

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Discussion Starter · #14 · (Edited)
Yes, the resistance was the same on all cyl.

Yes i see the part nr, but someone said in the last thread that coils from M60 and E36 M3 also worked?

The reason im asking is because i see 3 of my coils has a different partn number :) Which belong to M60 engines(840/740)
 

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Crzy, I didn't mean the resistance (ohms) of the coils, I was refering to the resistors in the dme / ecu as mentioned in post 2 here - http://www.m5board.com/vbulletin/showthread.php?t=116658
I'm think that your dealer might of given you the wrong coils. You should ask them to check and make sure the coils they supplied can be used on b38 engine.
You also need to be sure that you have no vacuum leaks and that you have no fuel problems with pump or injectors - It has been mentioned before that the rubber washer / o ring fitted to the injectors can perish and cause vacuum leak.
 

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Discussion Starter · #16 · (Edited)
No i havent checked the ecu because the car runs fine when its cold? Is it difficult or can i ohm the coil cables?

Okay, is it hard to check this things, or can i spray startgas and listen for change in the idle?

I think i have to ask a buddy of mine that is alot better than me for help :(

Edit: The dealer said it would work, and the 2 coils i now have works?

I think i'll wait until i get the 4 coils. BMW thought it could be a coils since 2 of them are 16 years old, and the car is fine when its cold.

"A warm coil isnt the same as a cold coil" he said.
 

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Crzy, well resistance does increase with temperature so maybe the old coils have died. Have you tried unplugging the old coils one at a time when the misfire is happening and listen to see if the misfire gets worse or stays the same ??
I agree, you should get some help from a good mechanic or someone who knows more than me and you.
 

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Discussion Starter · #18 ·
Yes, so it's unlikely its something wrong with the ecu then?

No i havent tried that yet, because i have the last 4 coils here on tuesday, and then all 6 are new :) I think its a good investment either way.

But maybe i'll try unplugging coils one by one tomorrow and see :)

But the most irritating thing is the surging when im driving.
 

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Hi,

I'm watching and waiting for your results to this problem - I have a similar sounding 'surging' going on and have had since buying the car a year or so ago. Mr Faz has checked for any fault codes and there are none - I discovered I had the wrong plugs fitted and changed them for the correct ones - this seemed to help a little but not completely - the symptoms are a clean and even idle hot or cold, smooth and even pulling when cold but noticeable surging on partial throttle when hot - it may or may not be surging on full throttle when hot, it's difficult to tell with all the power being put down.

My next port of call is a full service and inquisition from Mr Farrell when time and money dictate

Good luck,

Sharkfan
 

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Discussion Starter · #20 ·
Now i have no idea again! :(

I changed all the coils as i said, and the car is maybe better i think.

When its cold the engine is 100% perfect, but when it starts climbing above blue it starts hessitating \ jumpy.

why is the car perfect when its cold?

Its no oilspills in the plug sockets, and the car works good on full throttle even at warm.

Tried Injector cleaners, cleaned MAF, Borch Sparkplugs etc.

Anyone? I havent checked with another ECU, but the engine works perfect when its cold?
 
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