Trying to track down the source of this hesitation/loss of power/stuttering/bucking

[mleonardo]

I've got an 89 325ix. I recently noticed an issue with bucking or hesitation at certain points on the power band.
What makes this issue terribly confounding is that it doesn't always occur at the same RPM, depending on the gear I'm in, and throttle position doesn't seem to have anything to do with it. It occurs around 6k RPM in 1st gear, 5k in 2nd, 4k in 3rd, down to about 3.5k in 5th. The ignition system on this car is new-ish, as are many of the fuel system components. I've tried spraying contact cleaner on both ends of spark plug wires, and that seemed to make the problem better, but not gone.
I don't want to throw money at this issue, but I would like to solve it. Where do I go next? I was thinking of replacing the ignition coil, as that hasn't been replaced during the car's 216k-mile life. Is there something obvious I'm missing? Any help is much appreciated.

[modernist]

Crank position sensor

[mleonardo]

I sprayed the CPS down with contact cleaner, as it was pretty dirty, but that didn't seem to do anything. How can I test to ensure it's operating correctly?

[mleonardo]

Well, I have a new CPS in the mail from Turner. Will post back with results!

[redlightpete]

If you haven't already, check the motor harness wiring connector under the intake manifold. It can get really corroded by throttle body coolant leaks.

[mleonardo]

If you haven't already, check the motor harness wiring connector under the intake manifold. It can get really corroded by throttle body coolant leaks.

What's the best way to get to it; what should I be trying to remove?

[redlightpete]

Check out this link:

http://www.bimmerforums.com/forum/sh...lug-DIY-Repair

If it is causing problems, it will probably look very bad. The pins and sockets will be green or black. If it looks ok, you might spray some contact cleaner on it, but start looking elsewhere for your problem.

[mleonardo]

I replaced the CPS, routing the wire across the front of the engine. Will this present any problems for long-term use?

[modernist]

As long as the wire doesn't get eaten by anything, it should be fine.