Squeaky distributor = surging/misses

A problem has returned to my '83 400i automatic, that it had before I bought it in February '12. There are two symptoms. One is that the distributor intermittently emits a rough-throated squeaking sound, rather like the sound a small electric motor will make when it needs a spot of oil. The other is that, under light acceleration and at cruise, the engine hunts or surges.

What I have done: I took off the distributor cap and removed the rotor. I gave the rotor contacts a shine, using 1000 grit sandpaper. I also cleaned the interior of the distributor cap with a microfiber towel soaked in lacquer thinner. I carefully reassembled the rotor to the shaft and seating and screwed down the cap (three screws).

One thing I noticed is that the shaft that the rotor sits can be pulled in and out, with at least 1/4" of play. Is this normal?

(Bonus auto shop tip: if you put the ignition key in "run" position to roll down your car's windows and forget to turn it off, and then you jam a microfiber towel soaked in lacquer thinner inside the distributor cap, you get (a) a nasty electrical shock to your fingers and (b) a spectacular fire (for its size), as the lacquer thinner ignites Also, a burning microfiber towel is hard to extinguish. Stomping on it doesn't work. You'll need a bucket of water.)

 

Maybe if I narrow the question, someone will know. Is is normal for the distributor shaft to have 1/4" (1 cm) play: that it freely moves up and down this much, when you pull on it?

Before I bought the car the seller pointed out the squeaky sound coming from the engine bay. He thought it was the transmission, which had just been serviced. He took it back to the transmission shop. He reported to me that the transmission shop identified the distributor as the source of the squeak. He said they found something loose, and they tightened it. As I recall, he said the loose item was a magnetic something or other. I remember the reference to "magnetic," but not the full explanation. Does anyone have a guess what this loose, squeak inducing, item could be?

 

I spoke to the tech at the transmission shop and he told me what he did was to re-align the distributor cap and tighten it down evenly. It was the rotor hitting the cap that was causing the noise. I will give it a try.

BTW the tech called the distributor a "magneto." That's where the reference to something "magnetic" came from. I don't know why the man calls a system with an external coil a magneto, but I did not argue the point.

 

Last evening I removed the distributor cap again and carefully set it back in place and snugged and tightened the three screws like a surgeon at work. Happily this made the noises go away, and the surging as well. I was pleased. But after I got the oil temp up, I gave it a 6000 rpm burst in 1st and a new high pitched squeal set in at about 5000. Also, the surging has returned.

I will re-try the off-again, on-again routine on the cap, and hope for the best. But I would appreciate any insight any fellow F-Chatters may have on this problem. I'm sure "throwing parts at it" is the wrong solution. Ricambi's price for all the major dizzie components is "call" -- http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=3324 -- which I take it to mean, call the bank about taking out a second mortgage on your house.

Also, regarding the end play on the distributor shaft, I measured it with a calipers and it's about 0.1". Is that normal?

 

I have decided the distributor and the distributor cap are not the source of the surging or the squeaking sounds described in the original post. Rather, these problems were caused by arcing between the coil tower and the ground post on the coil. Each time this happens the arcing emits a tiny "squeak." At 2,000+ rpm the squeaks blend together into a continuous tone. I believe this arcing also would interfere with a good charge getting to the spark plug in random cylinders, leading to the missing or surging that I was observing.

If you have an MSD 6A, you will hear this squeaking sound when you do the paperclip test. The paperclip test is MSD's recommended test of whether the unit is working. With the ignition key OFF, you pull the coil wire off the distributor cap and you stick a Phillips screwdriver in the contact and place it 1/4" from a ground, for example a cam cover nut. Then you take a paperclip and bend it into a "U." Then you pull apart the two-wire electronic trigger plug at the MSD unit and stick one end of the "U" into the female half of the connector and you tap the other end of the "U" on the other connector. If the unit is working a spark will jump from the screwdriver to the ground, and it will emit this squeaking sound.

I reached these conclusions yesterday when my car just quit completely. One theory I had was that the distributor rotor had come loose. I took off the distributor cap and of course the rotor was fine. But I noticed when I moved it back and forth, clockwise-counterclockwise, I could hear that squeak. That was when I noticed the arcing at the coil tower. I rearranged the ground wire connector to maximize the distance of its outer edge from the coil wire boot, and the car started. But it died again and would not restart. So I got an old coil out of my garage -- it is a Pertronix brand coil formerly used in my '65 Mustang -- and swapped it in and the car runs as good as ever.

BTW the problematic coil is an MSD Blaster 2. I know I'm in a minority but I have had a lot of bad luck with MSD spark boxes and now with this coil. To be fair, the coil problem might be a coil wire problem: that the cable running from the coil to the distributor is the source of the arcing. If the Pertronix coil doesn't repeat the arcing problem, I will tend to think the Blaster 2 was the source. But it could still be the wire. Just to be sure, someday I'll go to the Pick n Pull and get some other wires.