BTW, the car is a '98 model and only done 128 000K's so the injectors should still be ok...I'll try the nulon anyway and see if that makes any difference, I'll also see if I can get my hands on an oscilliscope to test the O2 sensors...
Thanks to all you guys who wrote in... its a big help...I'll keep posting any progress I make...

Guys...have had no luck, had twin 2.25" exhaust system fitted and got the guys at the shop to check 02 sensors, they said all good...something that I thought might be worth bringing up is the fuel regulator. I'm assuming this is the little doovy on the rear of the fuel rail with the red vacuum line attached. Should I notice a difference when I disconnect the vacuum line ? I'm certain the car is definitely over-fueling as there is heaps of black smoke when you gun the throttle....not to mention the miss...starting to really peeve me...HELP

I would also change the fuel filter.
One of mine was so blocked I couldnt blow air through it.
Ryco Z373 fuel filter for an EF/EL series.

Ok guys...maybe this is progress...I disconnected the MAF sensor today and ran the car....the miss and black smoke disappeared !!! Although it was well down on power (would the computer retard the timing or decrease the fuel flow if the MAF sensor is not detected?). Would this indicate a faulty MAF sensor ? I'm hoping that this is the case, I don't have another MAF handy to try but I'll see what I can find...be interesting to know what others think...it would seem to me that the MAF may be sending a higher than normal reading to the ECU and causing overfueling...possible ?

Meant to ask...does anyone know how to diagnose an MAF sensor ? Resistance values, voltage values...what wires to check ?

A faulty MAF could lead to a very lean burn which can lead to pinging which of course is not good.
Disconnecting a faulty MAF will cause the engine to run rich, which is a lot safer to drive around on.
If you have access to diagnostics then run it and see what codes you get.

When you disconnect the MAF it will generally run very rich, around the 10-11:1 AFR range, and the timing is locked to 10 degrees (from memory). Generally when the MAF sensor stuffs up, the AFR's will go lean. Going lean can also cause black smoke or raw fuel out the exhaust, and would also explain the hessitation and miss, but without an actual AFR reading it is hard to tell what is going on. I would get it up on the dyno and get them to run the AFR's at idle, cruise, partial and full throttle. If it is running lean I would guess its the MAF, if rich then possibly coolant temp sensor (ford already said this, did you check or replace this) or O2 sensors.

I'm not wanting to sound prudent, but isn't black smoke and raw fuel a definite indication of a rich mixture? When the car runs it blows quite a lot of black smoke and smells very rich...it is also leaving very sooty deposits on the stainless tips...

I have checked all the sensors (bar the MAF as I'm not sure what wires or values to look for...) and the only one that seemed to give a lower voltage/higher resistance was the Intake Air Temp sensor...disconnecting this didn't change anything though....

Yes generally black smoke + fuel smell = rich but if the engine goes lean and misses, it will also dump unburnt fuel out the exhaust. It is fairly hard to test the MAF, you will only probably be able to tell if it is totally stuffed. The MAF sensor body has pins A,B,C,D labeled on them, C is the signal return wire. If you tap into that, you should see voltages around 0.8v at idle steadily rising with revs. Problem is that a change in voltage of even 0.1v is a fiar change in airflow so unless it is way off what you expect then you won't really know if it is working properly or not.

Rightio...I found some typical values that the MAF should return and compared them with my own...

----------Typical------Mine-------
@idle------0.6V------0.9 to 1V----
@32kph---1.1V------1.2 to 1.3V---
@64kph---1.7V------1.7 to 1.8V---
@96kph---2.1V------2.2 to 2.4V---

I don't know how sensitive the ECU is to these voltages but the values I found would seem reasonable to me except for the idle maybe...geez...it's never simple is it ! Can anyone tell me if these figures are fair...? Would 0.3V cause a miss...too much fuel ?? If they are ok, I'm back to square 1...sheesh..thanks for the explanation too EDXR8...

Those seem reasonable to me. As I said previously, I have never heard of a bad MAF causing rich running, its nearly always lean. Also to an extent, the MAF signal is over-ruled during idle and cruise so AFR should always be around 14.6, but I am not sure if yours is rich at idle/cruise too or just under load.

When Ford said it may be the coolant temp sender, did they test anything or was it just a guess. A dodgy temp sender will definitly give you a globaly rich condition, and other than O2 sensors is the only typical reason I can think of for the engine to always be running rich. It may pay just to swap it, from memory they are only around $20 new.

EDXR8..thanks for all the posts dude, has helped me rule out a heap of things...thanks to everyone else who wrote in also...BTW I checked the Coolant Temp Sensor myself after Ford suggested it...the voltage is in range. I will now roll over and let the Ford corporation take control...will book it in for this coming Friday and see what they can find...sad sad defeat...what a bugger !!!

Righto...an update, didn't bother with Ford as they're too busy and can't fit me in for the next week anyways...so I bought a secondhand MAF sensor from "offyaguts" for $60 delivered, which I'll get on Monday. I'm fairly hopeful that this will cure the problem...if it doesn't then its gonna have to be a Ford workshop booking to make...will keep posting...

Well despite the high hopes and all....the new (read secondhand) MAF made no difference, the car still has the same problem...bugger...

Windza,

All of the above are good suggestions and I'd certainly change the fuel filter straight up when buying a car.
Something else to check is the integrity of your grounds. Start by checking your block to battery negative...it should be zero ohms. Also check your HEGO ground is intact and solid(it's at the back of the intake manifold).
Have a look at the tuned resonance device(that curly thing between the MAF and T/body) on your inlet tube. Check to see that it hasn't been crushed (usually on the underside by overtightening)allowing the engine to ingest unmetered air.
Also check your TPS(for the EEC not the trans) voltage. Ive seen cases where the TPS plugs have been switched resulting in a 0.7v idle voltage to the EEC. Whilst this is acceptable normally, ideal throttle response is achieved when the TPS is as close as possible to 1 volt without going over.
So elongate the bolt holes in your EEC TPS to allow adjustment of the pot to give a 0.98v reading with a closed throttle.
Also check your base timing, it should be 30 degrees. You can usually afford to bump this by a couple of degrees if your engine isn't too carboned up and you use good fuel.
Also check your PCV system. I once fixed a 5.0L that worked itself up into a rolling idle because some knob head stuffed a ball bearing down the crank case breather hose!?!
I have one question; Did any of the plugs you removed show any different signs of combustion than the others?

Pete.