Failed ignition rotor

[911/914gary]

While cruising Sunday, on one of the nicest days I've seen for months, my car lost power, misfired and died! Fortunately it turned out to be a blown ignition rotor. What is odd is that I had a new rotor and cap installed from a major tune up about 3K miles ago. My question is what would cause the failure of the rotor in such a short time? The distributor seems OK. The shaft feels tight radially and has about 1/16 travel axially. The distributor cap looks all right except for the carbon build up on the contacts seems heavy. Is this typical? Or could this come from a failing rotor.

[bigchillcar]

What exactly do you mean by blown? Was it obviously damaged physically? Do you have an aftermarket coil too hot for your distributor? Just a quick wild guess.
Ryan

[911/914gary]

Bigchillcar:

The rotor was physically damaged. The rotor's attachment to the shaft and the blade were fractured. The car's ignition is stock, no hot coil or performance chip. The distribor cap was seated tight and true.

I did hit the "on set" of the rev limiter during a hard acceleration recently (I could feel the ignition beginning to cut out). However nothing abnormal was noted after this. I wouldn't expect this to damage rotor.

What are the typical type failures associated with a distributor? Is this a sign of something bad!!

[Rouxzy]

I've had this happen to me twice on two different vehicles. Turns out that it was just faulty rotors. Each vehicle ran just perfect after putting in a new rotor.
Tom

[1.2gees]

This just happened to me on my 944 turbo (soon after I rebuilt the engine at which time I replaced the cap rotor, plugs, wires, coil, etc.). I think it's likely bosch has had some quality control issues, or maybe just a feak incident...
Ahmet

[k9handler]

I have had this happen on other vehicles due to cold temps.
I had run the car and parked it when it was warm, and the air temp outside was not too cold. then after a rapid drop in temp, I went and attempted to leave in the morning and the car would not go at all. It turned out that the rotor just snaped due to the condensation and ice that formed on and around it with the temp drop...may not be the case since you are in the land of sun, but for some here it may well apply. That's my .02 cents worth.

[911/914gary]

OK...the consensus is that this is not an uncommon occurrence and that Bosch may have had a quality problem with rotors. I won't concern myself with the rest of the ignition system.

However I am concerned with the FOD (debris) inside the distributor. I got all the metal and most of the insulator material out. There is a good chunk of material I can't account for. (See photo) Should I be concerned? The material seems vary brittle and may pulverize (I hope) inside the distributor's mechanics

[rcwaldo]

Does your distributor have the dust shield? If so, that would prevent the debris from falling into the mechanical advance mechanism.

I hope this doesn' t happen again.

Chris

[Early_S_Man]

Gary,

There are two possible problems that can cause interference problems between the rotor and cap ... both can cause damage.

1. Excessive end play/float due to worn/missing phenolic washers on distributor shaft. There have been documented cases of end float approaching 0.125" due to missing fiber washers ... should not exceed 0.002" under normal circumstances!

2. Worn 'oilite' bushings in distributor body ... causing excessive radial play at shaft.

I suggest pulling your distributor out at TDC #1 after marking rotor position on distributor body with permanent marker. Clean distributor thoroughly with Brak-Kleen or similar degreasing solvent ... then check for excessive vertical or radial play in distributor shaft.

[Tim Polzin]

Pull the felt out of the top shaft and make sure the circlip is still in place. If not, you may get too much endfloat.

Tim