Odd that it is 1-3-5. My guess is electrical only. Anything else would affect all cylinders. I would also guess not CPS or ICV. Other than that I shall just wait till someone else comes up with the fix and learn something.

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Good - Fast - Cheap: Pick any two.
Current:
E23 735i; E30 318i; E32 735iL; E38 735iL; R50 Cooper; R55 Cooper Clubman.
Previous:
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i