Idle miss when hot / bad fuel consumption. 10 months on......

[Cam]

Ok, so as many of you know I am traveling OZ in my AU. I've now been chasing this issue for 10 months and am at my wits end.. Sorry for the long post, just wanna give as much info as possible, as I rely on my car very heavily.. Car is a AUII fairmont wagon.

Description: as the car gets warmer it gets a very pronounced "miss" at idle. Once the miss starts the car seems to loose power and fuel usage skyrockets. The miss is NOT consistent so it can be like brrrrrrrrrrdbrrrdddbrrrdbrrrrdddbrrrrrr at idle (I hope y'all making that noise in your head). I can be sitting at some lights and The the car is fine, next set of lights it goes bad. And visa versa.

I recently did a trip (without my van) from Brissy to Newcastle (admittedly I have a roof cage, and had 200kg of stuff in the back) and all highway driving (and driving nicely) I ended up with 13.6l/100. I never ventured more then 2km from the highway the entire time. When I first hit the road my consumption (based on the fairymonts l/100k calculations) will sit happily in the 9.0-10.9l/100 range, after a couple of hours of driving it's ramping into the teens..

I HAVE noticed that under light load the instant l/100 often goes (example) 10,12, 10, 11, 38, 42, 10, 11 and so on.

So far, I have changed... (last 8000km) plugs, leads, coil, fuel filter. Last 3500km - 02 sensor (now done twice), intake manifold gasket, CHT sensor, battery terminals. Last 2500km- tps*, iat*, map sensor,* (* = second hand) fuel pump, replaced collapsed rear muffler, second 02 sensor, cleaned TB and isc again, Pcv (now twice, just ditched metal one for a genuine ford one), compression test (185-188 all round dry test). Most recently I've had the car checked for fault codes, there was a fault for the tps that he cleared, and then confirmed it was operating as expected. He did mention the 02 sensor seemed slow to respond, but obviously was unlikely to be the cause of my issues. We also found the CHT voltages were way below what they should be, around the .4v despite it showing operating temperatures of around 88deg in his workshop. It's also worth mentioning I do seem to have some pretty serious blowby, thus why I swapped pcv for a genuine ford one.

He feels that because of the symptoms I have done a headgasket (between 5/6, despite no coolant loss / contamination). Or the CHT sensor is faulty.

So, I'm left with... Faulty ECU (read stories of ecus killing coils), leaky / blocked injector or fuel rail, fuel reg going AWOL, crank angle sensor, the second hand iat, tps or map sensor were rooted (seems unlikely I'd have the same issue, all tested ok), some kind of failure (bent rod, sticky valve etc), bad earth (adding another earth point just in case, seems unlikely IMO), or a blown head gasket.

The issue I mentioned earlier with the instant l/100 going off the scale makes me think it's electrical. It takes a lot of throttle at 100km/h to get it to read upwards of 40l/100, so I'm 100% sure it's not me slightly moving my foot..

I feel like burning this thing and buying a BFII wagon, so for eff sake someone help me before I do it!

/end rant
Cheers,
Cam