So i am currently, and have been for some time slowly chasing a reasonable fuel consumption. I have read a few topics here on fordmods but i thought i would see if there are any specific answers that a few would be able to provide.

As a history, i started out with about 38L/100km city and 12 for the highway. A hotter thermostat brought that down to 28 (!!!!) pretty quickly. Currently i am averaging about 25 no matter how I drive, luckily it isnt too far to get to work.

Basically every sensor except the TPS has been renewed, dizzy cap and button replaced a while back at a workshop. I have just tried a spare fuel pressure regulator (condition unknown) just for curiosity's sake. I just got a reco 4spd installed as well.

My thoughts at the moment are to replace the coil, in case there is a miss from weak sparks and then after that to get the ecu checked. As far as i am aware, there are not any leaks in the fuel system either.

So:

A. could a miss or timing troubles cause the engine to waste this much fuel? (Presumable unburned)

B. Could a worn set of timing sprockets and chain have this much impact?

C. Engine compression. I have seen test results from a year or two ago that were all just in spec. If it has lost some since, would that be something else to think about? I am definitely hoping not to have to pull this old motor down. (360000km).

Any other tips are appreciated. From what i can see as well, my IAC circuit has some fault as well.

Any info is GREATLY appreciated! Cheers, Andrew

Oh yea. 95 XG pano, though i assume that whatever issue i am hunting for is pretty much universal rather than engine specific..

When was the last time the O2 sensor was changed?

It wouldve been about 6 months ago. I head a heag gasket blown so i relaced that and the cat after it was replaced. Around the same time I changed the leads, plugs, MAP and coolant temp sensor as well.

What gets me is it seems to run smooth above idle, maybe a bit sluggish but Ive never driven another older falcon 6 to compare it to.

so whats the idle like? rough? could have a vac leak

Did you use a cheap ebay hego or a genuine item? I ran some Ebay ones and got horrid results, I would be looking very closely at the hego's as the symptoms you're describing are very similar to a failed sensor. Failing that, check your cat. Has it collapsed? With the I6 there is stuff all that mucks them up really.

In park and neutral it idles fairly smoothly, but it has always had a small arhythmic sort of shake to it as well. As far as vac leaks go- I tried water mist and found nothing, maybe TB cleaner is the way to go?

Could a bad brake booster have an internal vac leak? Or are they sealed? I do get an ocassional, intermittently hard brake pedal.

On a related note, IAC doesnt appear to work (torque converter load drops idle by around 300 - 400rpm, power steering rpm drops it as well). So idling in drive it is pretty shaky for the most part. When i get that fixed it will be a bit clearer. Currently i have wound the TB screw in and done TPS learn to get a decent idle for traffic lights, as a result though theres a bit of rev hang and hunting in P/N. That shaking at 200 rpm was more of a pain though...

(I have already renewed the IAC solenoid valve itself, is there a fuse or relay i should be checking out for that issue? Or maybe an easy way to check if there is a fault)

Use brake cleaner or tb cleaner. If your getting a hard pedal then you have a vac leak somewher

The sensor was from ebay, but I went for a VDO unit over the generic looking ebay ones though. Reckon it is worth a replacement for eliminating the cause? In the meantime i assume it can be tested with a meter, right?

Cat isnt an issue atm. Long story, but lets just say ill be getting a new one next time i go to the exhaust shop..

Cheers, Andrew

Duly noted. Ill double check for vac leaks soon. maybe that would explain decent consumption on the highway (round 2k rpm constantly) with woeful alcoholism around town when the lower revs are in use as well?

You wrote: "In park and neutral it idles fairly smoothly, but it has always had a small arrythmic sort of shake to it as well."

This would suggest the engine may not be running an all cylinders. Have your checked/replaced spark plugs?

A month or two ago i replaced all the plugs, none of the old ones looked burned or black etc. I will check again though. All the leads are new as are the dizzy cap and rotor. I will change the coil soon as well as I'm sure that could potentially contribute to a weak spark problem. As i mentioned it has pretty high kms so it wouldnt hurt to replace anyway.

I know the coil on these is in a prick of a spot, but I have done engine mounts from under the car so i think I should manage with the coil alright.

Cheers for all the responses, i will definitely keep posting up any progress to help out anyone who gets similar dramas. I will probably pull the hego sensor out and test with a mapgas torch/multimeter next week and see if that is reading correctly.

silly question, being a panel van, are you loaded up driving around? whats your tyre pressures set to?
tese 2 things will definatly effect it somewhat.

Not really. Most of the time it is empty other than a toolbag.

Diff oil is fresh, trans is new and i dont think i have any brake drag either, though i havent checked after the brakes have been working in traffic. Pretty sure theyre okay though.

and tire pressure?