I do not believe this is necessarily the case kms but you may be right. Missing or a bad Dizzy would not cause overheating... At least not to my knowledge.
It sounds like the overheating may have messed something else up such as overheated the distributor. I would try to figure out why it overheated first. How is your cooling system? Clean? Clogged? Is the cap sealing properly. Was it low on coolant? I would check all that first.
Start up the X when you are fairly certain it will not overheat and run a power balance test.
You can unclip the injectors ONE at a time or Unplug the Sparkplug wire one at a time which can be dangerous so be careful. The injectors are not dangerous just the sparkplug wires. Rubber gloves would be awesome.
Listen to the RPM or using a gauge or the Tachometer in the X to determine whether the RPM drops everytime you remove one. (If you use the tachometer you need a second person since you cannot be in two places at once). If it did NOT drop then you have a misfire in that cylinder. unplug it and re-plug it in multiple times to see how many times out of 5 it Drops and how many times it does not.
This may or may not send a CEL.
This test will tell you how much one cylinder is contributing. compared to the other.
Once you narrow it down to which cylinders are misfiring then you can determine the problem. Your X Dropping to 650 Rpm only sounds like 2-3 Cylinders are misfiring and they may not be a dead miss so it is a little harder to tell. The X idles normall between 700-750 Anyway so it is not loosing 4-6 Cylinders obviously since it is not cutting off.
Once you determine which cylinders are misfiring then then see what is in common.
A distributor going bad like KMS said can cause a WIDE variety of problems. 1 Cylinder dead... multiple cylinders dead... Multiple misfires....Random multiple misfires... The list goes on and on.
A Sparkplug Wire, spark plug and fuel in injector would cause only 1 cylinder to go down in either a Dead miss or partial misfires and is usally NOT random. Most of the time there is some type of pattern to it.
I agree with KMS about your misfire problem it could be the distributor bearing that many people have problems with or the coil. hose two sound more likely; however, I had a similar issue to this except that mine did not overheat prior to misfiring and It was caused by the wire and boot coming loose. It would randomly misfire then go away.
I am assuming you have not received a CEL so it sounds most likely like
Random multiple misfire Symptoms to me.
Random multiple misfires make it Extremely hard for the computer to count the Misfires and like 3/4 times will not throw a CEL because of how many are missing and how when.
Last edited by ShiftingSkys; 01-13-2013 at 12:59 PM.