3.4L V6 still backfiring on gas

[pato Lurker Find all posts View Profile Close pato]

G'Day all first post for me so go easy. done a quick serch.
So our 2002 3.4L V6 prado started backfiring on gas, we got the gas put
on when we bought the car (not injected gas) at 150,000km its now done 250,000km. when it backfirers it blows the lid off the air filter housing and the hoses off the air box. It's been in and out of the mechanic who put the duel fuel kit on over the last few weeks. new converter, new coil packs, new leads, new spark plugs, had the mixtures adjusted and tuned, comprssion test (all good), full service, fault scanner does't shoe any faults.

any ideas and feedback would be great

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

When does it back fire, is it when you start it up????

[pato Lurker Find all posts View Profile Close pato]

It backfires when ya taking off or powering up a hill. Never at idol. Also the day after we had all that work done and new parts put in we drove to adelaide and back (1400km) and it ran great powering up all the adelaide hill and over taking. It was about a week after we got home it started again when my wife was driving to work

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

I would say start looking at the fuel mix, something is not right there, it is acting just like when you start up a motor on gas, and have your foot on the throttle, it will back fire, blowing up your airbox in the worst case. so if it is when you take off from standstill as you say, it is getting too much fuel (gas) causing the back fire.

[mackayvx Advanced Member Find all posts View Profile Close mackayvx]

Gday Pato. Welcome to PP mate. Thanks for searching before asking bud. Good on ya.

Anyways, how sure are you the mechanic knows how to tune gas properly?

First things I think of is Dirty Air filter & Air fuel mix is to lean & Clean your MAF sensor.

Thats what i found on my 3RZ 2.7... It was backfiring also.... Not anymore though.

Happy new year. Drew.

[pato Lurker Find all posts View Profile Close pato]

Oops I forgot to put the new MAF sensor in the list of new parts I got replaced. Maybe it needs to be re tuned after it's first 1500km on a new converter. Thanks for your feedback.

[Playdoh96 Member Find all posts View Profile Close Playdoh96]

Hi guys just to add my thoughts, sounds to me like a the mixtures are actually to lean or a air leak after the mixer. I would get it checked out by a gas only workshop. Hopefully it's a easy fix. By the way the MAF sensor has nothing to do with the engine when running on gas, only petrol, so I can't see that to be the problem. Goodluck in getting your 90 better Kris

[mackayvx Advanced Member Find all posts View Profile Close mackayvx]

Hi guys just to add my thoughts, sounds to me like a the mixtures are actually to lean or a air leak after the mixer. I would get it checked out by a gas only workshop. Hopefully it's a easy fix. By the way the MAF sensor has nothing to do with the engine when running on gas, only petrol, so I can't see that to be the problem. Goodluck in getting your 90 better Kris

Hey playdoh. Good point mate about the MAF. I have never really thought about the position of it on the airbox in relation to where the gas is flowing in. Of course the MAF has bugger all to do with it.. Apologies for giving a bum steer.
In saying that it was one of the things i checked and cleaned when i was trying to get my tune right... Hey it even goes well on the old petrol too...

[pato Lurker Find all posts View Profile Close pato]

That reminds me, when the mechanic asked if I wanted to replace the MAF sensor he said it's got nothing to do with it backfiring but may of been damaged from the backfiring. I'm very confident the mechanic knows what he's doing. I'll be sure to get it back to him as soon as they go back to work. Everyone takes time off this time of year for some reason. Lucky buggers.

[croozza Avid PP Poster! Find all posts View Profile Close croozza]

I would only be using it on petrol till the mechanic comes back from holidays

[pato Lurker Find all posts View Profile Close pato]

Yep thats what will be happening. Thanks

[evilbofh Lurker Find all posts View Profile Close evilbofh]

Mine backfired a lot after it was in the workshop to clean the idle controller.
Turned out the clamp after the gas injector was a bit loose and after a backfire it almost blow off, making the car run like a dog...

Replaced the clamp with a new one an now the car runs find..

I would clean the MAF easy to do just buy a can of the cleaner from repco or supercheap and unscrew it and spray..

Backfiring happens with all non injection type LPG systems so I would recommend getting a backfire relief valve installed on the air filter cover. I've ordered one from ebay.. http://www.ebay.com.au/itm/221119779666