Help! Hi everyone! So I've been desperate for almost two years since my 87' E30 had an engine problem and I decided to swap my 1.6 carb M10b18 for a 1.8 EFI M10b18 from a 318i. At the time the guy that used to run the workshop told me it'd be a quick swap and EFI was definitely the way to go. Turns out, gta6 is almost out and I still don't have my car back. It starts and runs, but two cylinders are misfiring (compression test sais they are ok, spark plugs are new, spark cables are fine too), the gauge cluster is not responsive, besides the battery light aaaaand the car is killing all the batteries. I've changed and cleaned all the ground wires, replaced all the bulbs in the gauge cluster. So my guess is that the guys didn't connect properly the c101 plug. What would be your guess? Also I've made a chart with the current state of the c101 loom that I'll post here. I think the guys pretty much tested and verified all the mechanical components and at this point I think it's safe to say that the problem is most likely electrical, as they don't have an in house electrician. From what I can tell, the the c101 body loom has a pin 9 for the tachometer, but the engine loom is lacking it. On the other hand, the engine loom has the pin 16 for the diagnostic plug, where as the body loom is lacking it. Would it be possible that messing up these two connections is causing all those sorts of problems? Plus I noticed that they cut the pin 20 ground wire but didn't properly isolate it. Thank you all in advance!
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Last edited by andremlanca; 01-16-2026, 06:25 AM. -
i'm not familiar with the m10 version, i do know there are a couple versions of the 6cyl c101. not every wiring harness is gonna match. when doing engine swaps there are 2 different c101 connectors used depending on how the original 6 was wired. a lot of guys do their own pin outs to avoid issues. you may have to do the same.
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