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Old 27-11-2011, 01:34 PM   #1
5.8
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Default Au II falcon LPG backfire

A mate's AU2 4.0 litre falcon had a backfire on LPG yesterday. It seems to be now running an about three cylinders even on petrol. Any ideas on what might be the problem, maybe the coil pack? and any ideas on what may have caused the backfire. It happened when accelerating from a standing start.

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Old 27-11-2011, 02:10 PM   #2
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Default Re: Au II falcon LPG backfire

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Originally Posted by fo,mo and co
A mate's AU2 4.0 litre falcon had a backfire on LPG yesterday. It seems to be now running an about three cylinders even on petrol. Any ideas on what might be the problem, maybe the coil pack? and any ideas on what may have caused the backfire. It happened when accelerating from a standing start.
Its a bugger but you could try different leads in different spots (undo from coil pack and change) having checked all are OK. I can't see the aback fire would stuff the coil pack. I had to change my inlet manifold gasket as it was letting in air.

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Old 27-11-2011, 07:19 PM   #3
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Default Re: Au II falcon LPG backfire

Suggest MAP sensor may have been damaged; it's in the manifold just under the throttle body on those so a real pita :(
Also check manifold gasket and all vacuum hoses very carfully - spray degreaser around while it's running.
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Old 27-11-2011, 08:31 PM   #4
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Default Re: Au II falcon LPG backfire

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Originally Posted by mongrelEF
Suggest MAP sensor may have been damaged; it's in the manifold just under the throttle body on those so a real pita :(
Also check manifold gasket and all vacuum hoses very carfully - spray degreaser around while it's running.
Good call, mine has done that.
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Old 27-11-2011, 08:42 PM   #5
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Default Re: Au II falcon LPG backfire

Quote:
Originally Posted by mongrelEF
Suggest MAP sensor may have been damaged; it's in the manifold just under the throttle body on those so a real pita :(
Also check manifold gasket and all vacuum hoses very carfully - spray degreaser around while it's running.
spraying carby cleaner is even better you hear a definate change in engine noise if there is a leak
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Old 20-02-2014, 03:06 PM   #6
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Default Re: Au II falcon LPG backfire

A duel fuel factory fitted LPG falcon au2. Started bak fire recently, changed spark plugs, running ok then back fired, changed leads, running ok but two weeks later back fired again every now and then when engine is cold. Running ok when engine is hot or on petrol. Is it the mixture or coil pack? Any advice?
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Old 20-02-2014, 06:09 PM   #7
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Default Re: Au II falcon LPG backfire

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Originally Posted by bolebrand View Post
A duel fuel factory fitted LPG falcon au2. Started bak fire recently, changed spark plugs, running ok then back fired, changed leads, running ok but two weeks later back fired again every now and then when engine is cold. Running ok when engine is hot or on petrol. Is it the mixture or coil pack? Any advice?
It could be running lean. That also causes a backfire.

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Old 21-02-2014, 09:54 AM   #8
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Default Re: Au II falcon LPG backfire

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It could be running lean. That also causes a backfire.

GK
Thanks. Had mechanic looked at this morning. It was stepper motor got jammed causing too lean or rich and backed fired. Sprayed with CRC to release jamming and off it goes beautifully.
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Old 22-02-2014, 07:29 AM   #9
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Default Re: Au II falcon LPG backfire

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Originally Posted by bolebrand View Post
Thanks. Had mechanic looked at this morning. It was stepper motor got jammed causing too lean or rich and backed fired. Sprayed with CRC to release jamming and off it goes beautifully.
Glad you got it sorted with a minimum of fuss. It's great when you get a fix like that!

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Old 22-01-2019, 08:48 PM   #10
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Default Re: Au II falcon LPG backfire

Quote:
Originally Posted by 5.8 View Post
A mate's AU2 4.0 litre falcon had a backfire on LPG yesterday. It seems to be now running an about three cylinders even on petrol. Any ideas on what might be the problem, maybe the coil pack? and any ideas on what may have caused the backfire. It happened when accelerating from a standing start.
Had the same problem, I blew the diaphragm on the mixer.
Went to Jollys, got another mixer, easy fix.
You can check by unplugging the little air hose going to the mixer, if nothing changes that means diaphragm blown.

Cheers
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Old 23-01-2019, 07:14 PM   #11
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Default Re: Au II falcon LPG backfire

Alexs the original post was in 2011. Good update idea.
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Plastic Surgery 3 Watch this space ??? Living in AU Heaven
How 2's: Change rear view mirror, Install backfire valve, Change foam front seats, Install auto transmission cooler, Replace Trans Shift Globe, Remove front door Trim, Paint AU headlights, install door spears, Premium Rear Parcel Shelf, go here...
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Old 11-02-2019, 05:01 PM   #12
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Default Re: Au II falcon LPG backfire

Backfire on LPG?
My AU ute runs on LPG, and when it backfires, I always check the plug gap.
No more than .8mm, and all will be OK. Sometimes too many backfires will also damage the plug leads.

Ray

2002 AU-111 at 350k
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