Hey guys i need some help, im about $1500 in the hole, and as a uni student, i cant afford to stuff around too much more.

I recently purchased a 03 BA Xr6 falcon converted to dual fuel in 07. When i purchased the car, the previous owner advised that the car was running a bit rough, and was in need of a service. New coils, new plugs, and it still runs like s**t. the mechanic suggested i replace my cat which was damaged but still no fix.
I have looked at the service documents from Ford, and the car has been investigated for the rough idle since new which makes me believe the gas is unrelated to the problem.

The misfire is obvious as low revs when the car is on both petrol and gas, causing the car to shudder, and revs dropping to the point of almost stalling before jumping back up to normal. Also, at about 1500rpm the misfire is obvious, giving the car a slight shudder.

Ive read about taking the car into ford to check the software, checking the vacuum, throttle body, etc etc etc.
Can somebody please enlighten me which route i should take to diagnose the problem, because im sick of throwing money at the car, when its still running as bad as when i first got it.

Thanks

hi andrew.how is this issue going?? i have the same problem at the moment i was told to change plugs and coil packs and to make sure i get both genuine, this made little difference, what my mechanic did was un plugged the gas computer and unplugged the car battery for the day without putting the gas computer back in and the car ran on petrol like a dream, he then put the gas computer back in and it still missed on gas but not on petrol but said it wouldnt be long until the 2 computers get confused with eachother and the problem to come back. im not sure about your situation but my misfire was caused by the gas side of things, if you say theres a paper trail of problems before the gas conversion it may very well be something else, but for now it wont hurt to un plug the battery terminal for the day and see if that helps. i am throwing my gas conversion in the bin, oh and do not use e10 that s**t will F**k everything... hope this helps

Hey mate,
I too have tried to disconnect the battery, but left the gas ecu connected - my belief based on reading is that this allows the computer to relearn all its variables. This seems to have improved the problem on petrol, slightly however, sometimes at idles the revs are so uncontrollable it ranges between about 250 and 1200 rpm, almost stalling then surging, which makes parking and reversing slightly unpredictable.
I am thinking of getting the throttle body cleaned, then disconnecting the battery again to see if this remedies my idle.

You could have a blocked pcv valve pop it off the top of the rocker cover and stick your thumb over the end of the hose. If it doesnt suction itself to your thumb its blocked, other than that im not sure. Maybe a cam solenoid is blocked u can cleannthem out with brake cleaner and compressed air

There are so many things that can cause this.
Have you checked your Earths? - make sure there is no Voltage drop from Engine to battery, battery to body?

Have you guys checked the O2 Sensor?

The Petrol system will reset, but then will re-tune based on the o2 sensor. if your driving on LPG, and it was set up NOT to disconnect the O2 sensor from petrol then theres a very good chance the car learns how not to run on Petrol while its on LPG.

The LPG Problems can come from all kinds of places. Too much Air being bypassed in, O2 Sensor not working correctly, grounds not correct so that o2 presents incorrect voltage to LPG ECU etc

You seem to have taken care of most of the other issues - so Id start there.

Nigel

Hey guys thanks for your suggestions, i really appreciate the assistance.

I think i will allocate this weekend to doing a 'trouble-shoot,' testing out these suggestions. Nigel i have not tried any of those things as of yet. These service documents as per ford make me think the misfire is something to do with the software of the car, so I'm gonna take it to my closest ford dealership in geelong to see if they can check that out.

The documents date around a year after the car was purchased, so the idle has been a constant problem as far as i can tell.
I might also consider taking it to tullamarine where the original gas system was fitted so they can inspect it to see if its the LPG system as you suspect.

Thanks,

Andrew

yes nigel is right there is an earth strap from motor to chasis which is braided youll prob find its rusted out and there are also another 2 earths behind either headlight which are only thin but also important..