Backfiring Issue

[XStatic64]

Hey all,

Since i had the exhaust done it seems my car is backfiring out of the exhaust (not cool as it's got brand new cats haha!)

I've changed the plugs with new ngk platinums and changed the leads as well with top gun 8mm....

Only thing i can think of is O2 Sensors are bad or need to be cleaned?

I have disconnected the battery whilst doing the plugs so the computer would have had to re-learn what it can..

How hard is it to change O2 Sensors?

When i did the plugs i cleaned the MAF screen as well (had a bee or two in it :P) and put a new air filter in.

Eventually it's gonna get a mafless tune and otrcai but that won't be for a month or so as i need to save some cash.

Also to add, It seems it only backfires sometimes, normally when the car has been driven for a while (30mins +) and is most noticable as a jerk in power in 4th gear climbing a slight incline ie: freeway.

Another thing i should add is the check powertrain light has illuminated for a short period before but never whilst backfiring and has always gone after a restart.

Car is still running fine otherwise.

Cheers,

Andrew - XStatic

[wikky]

It just needs a tune by the sounds of it mate.

[XStatic64]

I had thought this myself too, check engine/powertrain had come on before the headers/cats were done too but am unsure i guess.

Will have to go and save some money for a mafless tune and otrcai i guess. No way in hell am i getting it tuned without doing the airbox, mafless tune would rule out a bad maf too i guess :P

I was planning on a tune/cai anyway so i guess this would be the first place to start.

Will have to speak to a tuner about it, they would know all too well about running rich i guess

[sleepa]

Probably running a little rich at certain points. The reason it happens after you have been driving a while is that the exhaust heats up enough to burn the unburnt fuel that finds it's way through the exhaust.

I had a turbo car that was running fairly rich, but it only popped and crackled after a good 30 mins of hard driving. However the other car I have, which has an LPG mixer system, snaps, crackles and pops all the time. A mixer system is harder to tune properly as some fuel always goes through, and with a big exhaust it amplifies that.

[sleepa]

I had thought this myself too, check engine/powertrain had come on before the headers/cats were done too but am unsure i guess.

Will have to go and save some money for a mafless tune and otrcai i guess. No way in hell am i getting it tuned without doing the airbox, mafless tune would rule out a bad maf too i guess :P

I was planning on a tune/cai anyway so i guess this would be the first place to start.

Will have to speak to a tuner about it, they would know all too well about running rich i guess

I am pretty sure that all early LS1s ran rich which is why you can pick up heaps of power when you get them tuned.

[XStatic64]

Yeah.

It's also hard to say if it's the catback or whatever that is causing the check engine light as i was game enough to get it put on 1 day after purchase of the car .

All in all I've made a post on enhanced automotive's forum section looking to get otrcai and tune done, hopefully he can lean it out a bit for me (safely) so it doesn't occur.

What you've said makes sense though Sleepa, Exhaust is only 2.5" twin, fairly standard on most gen3's around the place i guess.

[sleepa]

I have just put on a twin 2.5 inch cat back and have yet to check the engine light. It is on all the time anyway coz a sensor is stuffed, but I can check the codes and see if there is anything new from the exhaust on mine.

[XStatic64]

If you could that would be good mate. It occasionally illuminates, car runs as it normally does... Switch it off for a minute and it's off. That's what had me thinking O2 Sensors but the light came on before i had the headers/cats done, one would think when the headers/cats were done the exhaust shop would have cleaned/looked at the O2 sensors and at least told me if one looked bad. So i guess tune may be in order after all.

From what i understand checking the codes requires a Tech2 / OBD2 Scan device is this right?

[sleepa]

Yeah, I have one from ebay its an autel scanner, I can check the engine codes but that's about it.

[sleepa]

I just checked the codes on mine and I have no new codes, my O2 sensors are fine. The only code I get is the oil pressure sensor out of range.

[XStatic64]

No worries mate cheers,

How much was the scanner from ebay? Might look into getting one, sounds like a useful diagnostic tool.

Cheers

[sleepa]

It is the MaxiDiag US703, but you have to buy the one that is for australian cars, falcon and commodore, cost me $249