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5L backfiring thru airbox after start up 

 

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 Post subject: 5L backfiring thru airbox after start up
Posted: Mon Nov 17, 2014 7:10 pm 
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Age: 38

Posts: 5

Joined: 4th Jan 2010

Ride: 383 XD - 5L DF - 5L EF

Location: liverpool
NSW, Australia

my 1995 df 5L fairlane has a weird problem I have never encountered with previous 5L's iv'e owned, it starts perfectly like normal but for the first 2-3 minutes/ a kilometre or so, it develops a miss and backfires through the airbox under load until it reaches about 2000rpm then it just suddenly comes good and gets on song, it will do this like I said for about the first 2-3 minutes of driving and it doesn't matter if it is from a dead cold start or if I turn it off at a servo for fuel, once I refire it up it will backfire and miss for another 2-3 minutes, if I floor it helps by getting it revving but that's not really good for economy lol, I have put new plugs,leads and checked a maf out of my other 5L and it still does it, iv'e also taken the battery out and reset the ecu (the right way resetting the idle and tps) and still it does it, if it were dirty injectors it wouldn't clear up after few minutes im assuming, has anyone else had or know of someone who has encountered this problem? iv'e had a few reads of similar-ish sounding problems but most searches talk about lpg powered cars, mine is only fuel.
thanx in advance

 

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 Post subject: Re: 5L backfiring thru airbox after start up
Posted: Tue Dec 30, 2014 9:14 pm 
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Age: 38

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Ride: 383 XD - 5L DF - 5L EF

Location: liverpool
NSW, Australia

okay here's the update, like I said I swapped maf sensor, coolant temperature sensor, ignition coil, checked fuel pressure, swapped air filter and cleaned intake piping and throttle body, checked for any vacuum leaks, swapped fuel pump assembly all no difference and thank god I have my old unregoed ef Fairmont wagon to swap parts around or that would of been a waste of cash for nothing, turns out when I disconnect/pulled the HEGO fuse from the fuse block problem has gone away, so until tomorrow - well maybe a day or 2 after because new years and hang overs lol I am going to swap the HEGO sensors from the wagon over onto the fairlane and see how it goes with the fuse back in, my theory is when it is first started it is in closed loop only operating at the base set paremeters within the ecu's system and after about a minute or so when it goes into open loop the dud HEGO sensor is telling the ecu it's running rich so it adjusts the fuel and leans it out until the knock sensors override the lean condition and adjusts the fuel curve accordingly which takes about another minute or two to adjust, and then it runs sweet...... does that sound right to any of you EFI guru's, I only have a basic understanding of it... I'm old school and too lazy to get with the times lol

 

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 Post subject: Re: 5L backfiring thru airbox after start up
Posted: Thu Jan 01, 2015 4:06 pm 
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Ride: ford falcon au3 xr8

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the 50l don't run knock sensors..
my thoughts are a bad injector or dirty maf sensor. how old are the spark plugs?
but 02 sensors may need replacing, they are generally only good for about 100,000km
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 Post subject: Re: 5L backfiring thru airbox after start up
Posted: Thu Jan 01, 2015 6:24 pm 
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TFI module perhaps?
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