Ignition issues cylinder 2

[ACJJ619]

Hi guys, trying to diagnose issues with ignition in cylinder 2. M52 B28.


The problem is quite intermittent. About half the time the car runs smoothly, but half the time it's clearly on 5 cylinders (or just very lumpy). It often switches between smooth and lumpy whilst driving, as if someone is literally flicking a switch for a spark plug off and on.


It threw a code for ignition coil cyl 2 so I replaced it and the code hasn't come back, but the problem remains.


Have tried swapping plugs and coils with cylinder 2 and 1, but the problem always remains on cylinder 2 as shown in the INPA screenshot below:


635998


In this album, you can see all my analogue INPA values plus three separate videos of the car idling on the roughness screen. They were all taken one after the other, with no changes. Simply turning the car off and on again. This appears to show the cylinder struggling but not quite failing completely (which it did later in the day as evidenced when I unplugged the ignition coil and it made no difference to the running). Interestingly, cylinder 3 also seems to struggle in these videos.


https://imgur.com/gallery/4Clcmec


Also has new OEM crank+cam sensors.


Compression test showed 120 - 135 range, so all seems good.


All I'm thinking it can be is dodgy wiring to the ignition coil, a failing injector (no code though?) or a bad ECU?

[Eric93se]

I would clean your injectors. You can get your own ultra sound cleaner from ebay. Also on youtube there are ideas on how to clean you injectors with a can of compressed cleaner. But ultrasonic cleaning is should be done in conjunction. Or you can send them out, but it's a bit pricey. You can get a filter/pintle o-ring kit off ebay just be sure to get the kit with the correct pintles, they are larger for the M52 pink injectors (the orifice). Your power balance is all over the place, mine never reads zero for more than one cylinder or bounces all over the place. So you might want to treat your engine to a new set of coils if you havent already. A brand new set is like $50US shipped.

[Eric93se]

Here is a kit from the US that can ship to you. I checked the uk ebay and didn't find any good deals.

https://www.ebay.com/itm/BMW-I6-Fuel-Injector-Service-Repair-Rebuild-O-ring-Pintle-Cap-Filter-Kit/263897026169

[Eric93se]

220v 50w ultrasonic cleaner. I would clean one at a time, high power and only fill till it covers the top of the injector. Not sure what the best cleaning solution would be, if you decide to use something flammable be sure to run far from your home.

https://www.ebay.com/itm/30W-50W-Mini-Ultrasonic-Cleaner-Bath-For-Cleaning-Jewelry-Glasses-Headwear/223011302358

I've rebuilt my injectors twice but didn't have an ultrasonic cleaner at the time. The last time I had them out I cleaned all the paint on the bodies off with a paint stripper wheel and repainted them with an acid etch primer.

- - - Updated - - -

New set of coils:

https://www.ebay.com/itm/Set-of-6-Ignition-Coil-1994-2005-FOR-BMW-5-Series-More-C1239-UF354-12131748017/262488221634

[ed323i]

Or you can buy these remanufactured ones, and flow matched set of injectors for a little over $100:
https://www.ebay.com/itm/Reman-OEM-BMW-Bosch-6x-Fuel-Injectors-0280150440-Z3-M3-328is-328i-528i-2-8L-3-2L-/252956336193#shpCntId

And then you can sell your old injectors (would be fair though to let the buyer know you're not certain about their condition, especially if the new injectors solve the issue)..

[ACJJ619]

Before I try this, should I not swap injector 2 with another injector and see if the problem follows it?

Also, in the shed I have another fuel rail with green injectors from my previous M52 B25. Is that compatible? Could I try that?

[ed323i]

Yes, swapping injector is a good experiment to prevent throwing money at your car.
The M52B25 injectors, like the M50B25 injectors alas flow a bit less. You could still try it, as the DME will probably adapt quite quickly (I recently watched live INPA adaptation figures and when you let the car idle, and the oxygen sensors come online, within minutes it can completely relearn the adaptation values). After that it will also have to learn the adaptation values for the higher load cells in the fuel injection table in the DME. Best to not go WOT, as it will run too lean in the beginning.. I think the injectors flow just enough for the stock 193 HP (like the 192HP in the M50B25), but multiplicative adaptation values will rise to +15% or so I guess. If the symptoms disappear (after the DME has relearned everything) you can then buy or clean 328i injectors.

[ACJJ619]

I think I've found it!

I fiddled with the ignition wiring harness and was able to manipulate the engine running by just moving it around a tiny bit. I was able to turn cylinder 2 off and on by just wiggling it about a bit, so I'm 90% sure it's a dodgy wiring harness.

[ed323i]

Cool! That's great news. If you can find the spot where it's the most sensitive to movement, you could decide to open the wiring there and hopefully find the bad wire, and then solder in a new wire.
I believe the coils have a separate sub wiring harness (https://images.prussianmotors.com/empower/inv_000386.jpg) (which connect to the wiring harness with a plug), which can be replaced without replacing the entire wiring harness.. But I'm afraid the injectors don't (M20 and M54 have sub wiring harness for the injectors), but I'm not certain. Perhaps someone else can tell you that.. If it is a separate wiring, then you can go to the junkyard and get that part of the wiring and plug it in, and you're done, and you still have the complete factory wiring with no cables opened up and soldered.

[ACJJ619]

Fixed! It was the ignition coil wiring harness. I replaced the whole unit with a used one from ebay, super easy and cheap!

[ed323i]

Great! Congratulations!
Thanks for letting us know the results.