Discussion
Hi
I’m investigating a rough running issue.
Although it could be a vacuum leak, turning off and restarting the engine tends to cure the problem completely, so I conclude an electrical fault. Plugs are new. This engine (Alpina) uses old style M54 coils.
The problem is that the BMW ones don’t come with the rubber boots, so I would need to reuse the old ones which I’d rather not. The second problem is that Bosch, Hella etc now make these components in China. I’d rather not buy Chinese components if I can avoid it. Finally I have found a Dinan part that claims 10% more power than stock - I have heard that since the company was sold Dinan is not what it was.
What would you do?? Thanks for your advice
I’m investigating a rough running issue.
Although it could be a vacuum leak, turning off and restarting the engine tends to cure the problem completely, so I conclude an electrical fault. Plugs are new. This engine (Alpina) uses old style M54 coils.
The problem is that the BMW ones don’t come with the rubber boots, so I would need to reuse the old ones which I’d rather not. The second problem is that Bosch, Hella etc now make these components in China. I’d rather not buy Chinese components if I can avoid it. Finally I have found a Dinan part that claims 10% more power than stock - I have heard that since the company was sold Dinan is not what it was.
What would you do?? Thanks for your advice
Nothing wrong with those later Bosch/china coils fitted loads of them with no issues inc on the M54 motor, IME coil failure is made far more likely when used with knackered spark plugs (over loads the coil driver etc) my M54 is still on OEM coils @ 205k miles , your issue should flag up misfire fault codes if indeed you have a coil malfunction and quickly too the DME is smart on these engines reporting , and IME turning off the ign and back on again can resume function until the coil falls over once more 
read the scanner data if a misfire is reported swap coil from known good cyl and move the fault then you have your culprit if you move the misfire , live data / misfire counter is your friend here , vacuum/air leaks can be monitored/caught in short term fuel trim values
read the scanner data if a misfire is reported swap coil from known good cyl and move the fault then you have your culprit if you move the misfire , live data / misfire counter is your friend here , vacuum/air leaks can be monitored/caught in short term fuel trim values Edited by Sardonicus on Tuesday 26th May 10:58
It would seem unlikely 3 coils to go faulty all of a sudden
Were they just reading codes, or is there an actual running problem that lead to looking further ? Can you feel misfires ?
You say rough running, is it all the time ? only under certain circumstances ?
If all the time, it should make it easier to diagnose.
Were they just reading codes, or is there an actual running problem that lead to looking further ? Can you feel misfires ?
You say rough running, is it all the time ? only under certain circumstances ?
If all the time, it should make it easier to diagnose.
stevieturbo said:
It would seem unlikely 3 coils to go faulty all of a sudden
Were they just reading codes, or is there an actual running problem that lead to looking further ? Can you feel misfires ?
You say rough running, is it all the time ? only under certain circumstances ?
When misfiring the engine chugs and the check engine light comes on and stays on. However most of the time the car runs fine and then after a few normal ignitions the check engine light goes out again.Were they just reading codes, or is there an actual running problem that lead to looking further ? Can you feel misfires ?
You say rough running, is it all the time ? only under certain circumstances ?
There is no pattern to the rough running. If on cold start it chugs, a switch off, switch on again usually cures it
The engine has never been the smoothest, they are known for being a bit uncouth
Krikkit said:
Why would a dumb component like a coil pack (or rather, 3) be solved by a restart?
I had an intermittent coil failure on my S4, it would do it under heavy load and the car would shutdown that cylinder so that it ran like a tractor.Restarting the engine would resume normal service, until it shut down again. Apparently 'cylinder shutdown' occurs after detecting a preset number of consecutive misfires?
A new coil pack solved the problem.
As for rubber boots, are they absolutely necessary on this engine? and if so the old ones would surely be OK if not damaged and better than nothing anyway.
It's only likely to be a problem if the area is likely to get water on it - my Son had a Clio that had a tendency for the right-side scuttle drain to block with leaves etc. (as he would park under some trees at work) and so the water would overflow onto the top of the engine, specifically around the (no.4) coil pack. The water would then leak past the boot, fill the 'plug hole' and cause a misfire.
But I can't see that happening on, for example my S4 as the coils are well away from any water source.
Krikkit said:
Why would a dumb component like a coil pack (or rather, 3) be solved by a restart?
I would think with those symptoms you'd be looking at replacing the DME
Because they often soft fail on these engines so a cool off or restart can OFTEN have them working again but not ALWAYS and seldom for long I would think with those symptoms you'd be looking at replacing the DME
the misfire counter / algorithm is not perfect so you may have one cylinder misfire reporting/blaming other cylinders also (it happens) may be just cyl 4 for example, also check this ground / earth for integrity/continuity it shares a bolt/stud with the cam cover its the return for 4/5/6 cyl coils , it may be just loose I have seen some horrible workmanship/bodges on older BMW models (and I dont specialise) so keep an open mind , good luck Edited by Sardonicus on Wednesday 27th May 13:50
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