I've had falcons on and off for years and recently bought this dual fuel xh longreach with around 300k on it. I had the gearbox serviced and have just been using it to take the trailer to the tip and move a few tools around. Now after about 1000ks it is having issues.

Symptoms

Miss firing from the mid range up while driving - petrol and gas

Rough idle - though this is worse on petrol so I had put this down to injectors

Hard to start on LPG and Petrol

Leaking coolant from the coolant block at the front of the head

Low on coolant - though that isn't surprising considering that it's leaking

Plan

Remove coolant reservoir and clean it - hard to tell if the coolant is contaminated 'cause it's gunky

Fix leak on coolant connection to head? Not sure if it's worth it until I find the cause of the starting issues as I may have to take off the head

Compression test cylinders

Check plugs

I'm ok with tools, but I'm by no means a trained mechanic, so I'd love any advice that people are willing to give. In the past I've mostly let mechanics work on my fords but I have helped my brother do an engine swap and have done a clutch or two. I have also done a head on another car. I'm not really as cashed up as I once was now that I have kids and only one income in the house, so this will have to be fixed by me.

Thanks for reading...

I would suggest to start checking the ignition side of things. Check plugs, leads, ignition coil, distributor and the TFI module on the side of the distributor.

Does it get worse when that car has warmed up/hot?

+1 to compression test, the more you know the better you can troubleshoot.

If you can get your hands on a working coil/TFI module to swap them over, this could save you on money without buying everything and not have the issue fixed. Check coil first...the coil tends to fail with increase in temp, while the TFI module, if it fails your car won't start at all.

Regarding the coolant leak, where exactly is it leaking? Between head and block, or just at a hose?

Thanks phongus...

The coolant leak is between the head and the coolant block thing that has the thermostat in it. Looks to be where that joins the head.

Other than visual issues with the ignition is there a method that I should use for testing it all? Or do I have to have a known good coil and known good TFI. I'm guessing it's not the TFI 'cause I can get the car to run but not well.

Have a good look at the spark plugs - if you find a rusty one (or more) that is the one that is drinking the water. I had the same thing with a few E-series cars. If it is leaking, save your money and fit an AU engine - believe me, it's way cheaper than fixing a leaky head gasket, and it is a better engine as well.
Good luck.

Thanks sooty72...

What is the go with fitting an AU engine. Am I going to have do change the computer and wiring, or is a plug and play change?

Cheers...

I found this info... ford-4l-and-6-cylinder-f1/au-motor-into-el-falcon-t125575.html

What's the cheapest way to get an AU engine? Just buy an old AU without too many ks?

Go to the wreckers and by the lowest Km motor that you can afford.

Things required to fit AU engine to EF/EL (updated 15/02/14)

1) Sump needs to be modified to fit K-Frame, you can cut and weld the K-Frame but that is up to you, will need engineering after being cut. You cannot use an E Series sump as the sump is totally different to AU. There are cases of the E series sump being used but filler plates or large quantities of sealant were used, not recommended. Also you loose the advantage of the cross bolting of the AU sump when using the E series sump, one of the major strength points of using the AU Block.

2) You need to use AU/BF alternator or you will need to modify the block and drill and tap mount points to mount the EF/EL alternator.
If you use an AU I alternator you will need to change the plug for the alternator to one from an AUI as these are different from the Mitsubishi alternators.
Note: The AUII & III and BA alternators have the same plug as EF/EL.

3) Remove the Oil Drive Block where the Dizzy (EL) or cam sensor (EF) goes and remove the gear from the shaft and fit to your Dizzy (EL) or Cam Sensor (EF). This will then mean that the gears are matching and you should have no issue’s, there have been issues with dizzy’s failing when this has not been done. Some modding will be required to use the existing mount point, extra notch in the clamp plate or grind the tab off the Cam sensor.
Note:Do not try and drill hole in existing EF position on AU block, you will drill through the block.

4) You will need to use an EF/EL thermostat housing as these have your temp sensor and AU housings do not. You could use the EB type if you wish as this has an extra fitting for an additional sensor is required at a later date.

5) You will need to use the EF/EL BBM as the upper section is different to the AU. Also use the EF/EL throttle body as some of the plugs are different to the AU.

6) Use the EF/EL wiring loom.

7) You will need to tap the block on an AUII/III Block with an M12 1.5 tap if using the EF/EL Knock sensor. AUI is already tapped with the correct thread for the EF/EL Knock Sensor. If using the AU sensor you will need to modify the plug.

8) a) You will need to cut the EF/EL AC pump mount spacers down to 30mm to suit the AU block as well as shortening the bolts by 10mmm if using the AU alternator to suit the standard serpentine belt.
b) If using the EF/EL alternator with modified mounts you will not need to cut down the mounts and be able to use the standard Serpentine belt.
c) Alternatively you can use the AU alternator , standard AC spacers and a Serpentine belt from an XH (Slightly longer).

9) Use the EF/EL power steering pump. This is a direct bolt up. The AU pump hose connection is different to the EF/EL.

10) You do not need to change the Harmonic balancer for either EL (Dizzy) or EF Coil Pack.

11) If fitting to EF you will need to use your original Coil Pack or an AUI coil pack as these are different to AUII & III. (different plug) You can use an AUII/III coil but the plug with need to be changed as well as different leads.

12) You can use the AU head or fit you EF/EL head, that is up to you.

If it's just that little block that houses the thermostat, than that is an easy fix relatively speaking. Drain the coolant, pull the thermostat block off and replace the gasket. For extra seal, add some gasket maker blue/red on all mating surfaces. That should stop the leak.

I also suggest checking the coil first.

Since the leak was obvious I fixed that first and then decided to diagnose the other issue after. The problem was... once it was fixed the other issue went away slowly. I think it was just the leaking coolant dripping down onto the ignition that was stuffing up the running. Once it dried out we are all back to normal.

Thanks for all the help guys.

Good to hear you got it sorted!