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Weird backfires


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My car is a 2008 legacy gt with about 126k miles. Recently I was having issues with a misfire so I replaced cylinder 1 and 3's injectors with denso 656cc ones. When I first started the car it had a lower idle than before (less than 1) and when I accelerated hard, there was a loud pop, a loss of power, and maybe 1 minute later the check engine would flash for 10 seconds and then stop. Since then I have not experienced it again, but I also have not been accelerating hard. Now the cel is constantly on. When I looked at the injector tips they are slightly different but they both come from denso and both are 565cc. I don't know what the main issue is. Please help.
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You shall have all injectors identical or you will get all kinds of strange side effects ranging from the backfire you experienced to burnt cat and exhaust valves on the lean cylinders.

 

 

 

If it was a true "backfire" then it can range from the T-connector popping off to the intercooler being damaged.

 

 

A low idle - that's because the ECM haven't had time to adapt to the new fuel mixture. And if you have disconnected the battery then low idle is normal since the ECM has to re-learn.

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  • I Donated Too
Wouldn't be my choice to swap random injectors... as ehnils said it may well learn around it and behave but I would feel better if the injectors are matched. Maybe it doesn't matter maybe it really does but if you go lean on a cylinder (which is mostly what a backfire is) you can end up with more problems.
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I have never been able to replicate those backfires ever again. I switched out the other two injectors so all of them are the same but I am still getting the misfire code. Might be because I had fouled the spark plugs so I am going to check on them and replace them today.
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Keep track of the old plugs and compare them - they shall look the same.

 

 

And when replacing plugs also clean the coils with brake cleaner. Don't use WD40 on high voltage items since it leaves an oil residue that attracts dirt.

 

 

Make sure the connectors for the coils are good and connects properly since that's also a cause for misfires.

 

 

If you still have misfires then it can be a valve clearance issue.

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