part 1 the pain with the distributor started when two things happened from design viewpoint first there was need to fit the complete disti into the likewise tiny device it now is (other cars have coils separated etc.) second the disti with the attached engine was fitted into a likewise tiny engine compartment over the years i collected a lot of experience with this thingy the major troublemaker is HEAT. if you notice ...the front bank of our engines gets pretty hot, and even if you just drove around the block if you let your car rest, the heat is crawling up into the upper engine section and that is where the pain starts, and there's nothing much you can do about Now the distributors itself is assembled from a few different parts -there is the cap with its 6 attached wires to the spark-plugs -there is a rotor -there's an inner cap -there is a transistor-harness also called 'stator-assembly' or ignition control module (ICM) featuring one heavy duty transistor, and two hall sensors/transistors -crankshaft-position sensor 1 -camshaft-position sensor -two metal plates which generate the sensors input -then there is the coil function: the two sensors give away camshaft and crankshaft position to the ECU/PCM, this wise thingy does some algebra and decide when it's time to fire the sparks. firing the plugs mean there is POSITIVE potential on one side of the coil and the transistor shortens the circuit on the primary side of the coil to ground. That results in a high current through the coil with nothing much happening at this point except building up a likewise strong magnetic field inside the coil. then the transistor is switched off again, and in that very moment the magnetic field inside the coil collapses and creates a high voltage (less current) impulse on the secondary side of the coil. which is directed via rotor (if in correct position and clean) to the spark-plugs. this is normal operation now, why does it fail ? the coil is build from thin copper wire which is isolated with thin paint and winded around some metal core multiple times, finally put into some epoxy-stuff, or whatever that is. the goal was to build it that way, that the wire inside could not move, and that different layers of that wire do not make contact to other layers of that wires inside. NORMALLY that is the case .. .for quite some time. but then there is stress from both temperature and magnetic field's pulling forces and that results in slowly rubbing away paint on that wires in critical spots within the coil. so it starts to wear out without notice, with the result that either the primary side of the coil needs more current, or the secondary side of the coil does not produce enough voltage, or both. if the primary side (the side where the transistor is switching) consumes more current due to one or more hidden shorts within the coil it starts to run above specs the pain starts slowly without notice now there is this 'switching' transistor in the ICM (actually i never heard about a failing sensor so far) with a coil 'slightly' out of specs (you can't even measure that cause you don't know the specs) the transistor has a problem. due to too much load running through it it heats up. not at once...but slowly.. depending on the severness of the coils failure .. the only reason which keeps the transistor from failing at once is the fact that this transistor is a 15 Ampere trooper that normally can withstand 'a little too much' but if you drive around like this, you see it happen from time to time, that the whole assembly FAILS within seconds failing means that the transistor is not closing the circuit or that the transistor is 'tunneling' (seldom) and closing the circuit for too long. as an immediate result you see your tachometer instantly hitting zero, cause its directly attached to the ICM on the switching side of the transistor. this 'out of spec'- mode for the transistor causes permanent increasing damage to it, and you have an increase of stalls over the time. (another factor is the backfiring primary side of the coil which i not yet investigated in, but which i know is building up another high voltage impulse to the collector-emitter contacts) HEAT is the number1 factor in this the case that our probes engineers were smart enough to put the transistor INSIDE the distributor will grant you with a whole lot of fun with this coil/transistor combination over the years. both coil and transistor get too warm in operation and have no chance to cool down due to the disti's design. so you can change the transistor or the coil ... or both like Fords TSB says .. if you save money ... change just the transistor, and have the same trouble again in some time. changing the coil only will not heal the transistor... ..to be continued.. __________________ Tamara M Johnson ------- LINUX means rebooting just for new hardware part 2 so whatever you do... sooner or later you'll have that trouble again, cause there's actually no way to get the whole combination away from the #1 reason ...HEAT .... as far as i know there are 4 different ICM modules on the market 1. there was a version with plastic-encased transistor on the stator-assembly (this is considered to be the OLD version coming with 93 Probes maybe others too) this one i would say is crap 2. there is a 'modified'/improved version where you can SEE the transistor, but the transistor is still mounted within the stator assembly. this one i would say is the NORMAL one 3. there is a 'rumor' that there is a version where the transistor is on the OUTSIDE of the stator assembly. (if someone has the part-number plaese let me know) .. but i just see this one as a rumor maybe it's on mazda626 ?? i dunno 4. there is a version a friend of mine build for his car he took an old stator-assembly removed the transistor, put a bridge to pins 1 and 3, screwed the transistor to a PC-heat sink and mounted that on the outside of his air-intake ... interesting and easy-to-do mod .. but it's still in testing-stage __________________ Tamara M Johnson