Backfire at idle
04-29-2018, 12:33 PM
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Backfire at idle Hey I have a 2002 camaro z28. And 1 day I cranked it up with no problem and I was sitting to let it warm up and all of a sudden a heard a random pop out the exhaust like a gun shot. It never do it while I’m driving only when I’m at a stop light or parked and it’s always random never consistent. I changed the 02 sensor mas air flow sensor and plugs... what could be the problem
04-30-2018, 09:02 AM
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i doubt if this is normal at all.... it never did this and this is my 3rd ls car and I never heard somebody else car do this..
05-01-2018, 07:33 AM
#4
Welcome to the site. You are more than free to read through the thousands of posts to see that this happens as a normal occurrence.
The colder the environment you live in, the more this happens. (So, that may be why you haven't personally experienced this before.)
If you just replaced emissions components (the new MAF would probably be a bigger lever in this situation), you will also have to take the car for a long drive for the PCM to "relearn" the sensors and adjust your fuel mixtures. So, if you had a backfire before the relearn, that wouldn't be surprising or alarming either. Just take the car for a 15-20 minute drive on the highway and things should go back closer to what you are used to experiencing.
The colder the environment you live in, the more this happens. (So, that may be why you haven't personally experienced this before.)
If you just replaced emissions components (the new MAF would probably be a bigger lever in this situation), you will also have to take the car for a long drive for the PCM to "relearn" the sensors and adjust your fuel mixtures. So, if you had a backfire before the relearn, that wouldn't be surprising or alarming either. Just take the car for a 15-20 minute drive on the highway and things should go back closer to what you are used to experiencing.
05-01-2018, 09:31 AM
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Welcome to the site. You are more than free to read through the thousands of posts to see that this happens as a normal occurrence.
The colder the environment you live in, the more this happens. (So, that may be why you haven't personally experienced this before.)
If you just replaced emissions components (the new MAF would probably be a bigger lever in this situation), you will also have to take the car for a long drive for the PCM to "relearn" the sensors and adjust your fuel mixtures. So, if you had a backfire before the relearn, that wouldn't be surprising or alarming either. Just take the car for a 15-20 minute drive on the highway and things should go back closer to what you are used to experiencing.
The colder the environment you live in, the more this happens. (So, that may be why you haven't personally experienced this before.)
If you just replaced emissions components (the new MAF would probably be a bigger lever in this situation), you will also have to take the car for a long drive for the PCM to "relearn" the sensors and adjust your fuel mixtures. So, if you had a backfire before the relearn, that wouldn't be surprising or alarming either. Just take the car for a 15-20 minute drive on the highway and things should go back closer to what you are used to experiencing.
05-01-2018, 10:32 AM
#6
It may happen to a lot of cars but it's not normal and shouldn't be happening. There are many reasons for backfires in the exhaust but the shotgun sounding backfire is a large amount fuel igniting in the exhaust. Not the typical cackle backfire you might hear when decelerating of random pop of large cam. It could be a dirty injector dribbling fuel instead of spraying it. It could be an injector not closing all the way. Basically fuel needs to be a mist/vapor to burn properly if it dribbles in to the cylinder some of that liquid fuel is not burned and pushed into the exhaust where it builds up until the exhaust temperature get hot enough to turn it into a vapor where it will finally burn. (explodes) Quite different than a random misfire type backfire. I'm not saying that this is 100% the cause of your problem but it's certainly a possibility.
My friends used to drive down the road with a carb engine. You would leave it in gear while rolling along and shut off the ignition so it would pull raw fuel into the exhaust then turn the ignition back on and it would make one hell of a loud boom when that built up fuel ingnites.
My friends used to drive down the road with a carb engine. You would leave it in gear while rolling along and shut off the ignition so it would pull raw fuel into the exhaust then turn the ignition back on and it would make one hell of a loud boom when that built up fuel ingnites.
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05-01-2018, 10:57 AM
#10
I guess I should clarify something, The shotgun type backfire I was talking about in my previous post is one that is really freaking loud... Like being in the hood....duck and run because you think someone shot at you loud. If it's just a small backfire or random pop then that opens it up to many other causes like exhaust leaks and ignition problems and so on.
05-01-2018, 11:36 AM
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I guess I should clarify something, The shotgun type backfire I was talking about in my previous post is one that is really freaking loud... Like being in the hood....duck and run because you think someone shot at you loud. If it's just a small backfire or random pop then that opens it up to many other causes like exhaust leaks and ignition problems and so on.
05-01-2018, 11:50 AM
#13
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My jeep would do that when one of the injectors stuck, thats why I asked about the weeping injector, it literally blew the stock muffler wide open like a banana..
05-01-2018, 12:13 PM
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05-01-2018, 12:34 PM
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On mine, I ran the engine at about 2200 for 5 minutes ,, then let it idle for about 30 seconds and turned it off, pulled the plugs and one was soaking wet, pulled the injectors and the one that had the wet plug I could blow air through with a rubber tip on a air hose and about 25 lbs of air pressure.. Of course pulling the injectors on a 4 cylinder jeep motor is a 5 min job.
You could also use a bore camera and feed it through the intake, with power on and pressure in the lines none of the injectors should be dripping any fuel. (Engine NOT running! )
You could also use a bore camera and feed it through the intake, with power on and pressure in the lines none of the injectors should be dripping any fuel. (Engine NOT running! )
05-01-2018, 01:05 PM
#16
How many miles are on the engine/injectors? Might not be a bad idea to send them in to be cleaned/tested.
05-01-2018, 01:18 PM
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[QUOTE=LLLosingit;19888160]Yeah, That's why I replied above about possibly being an injector dribbling fuel rather than spraying it. Either debris keeping it from closing or dirty keeping the flow to a dribble rather than a mist. Either way it can cause raw fuel to enter the exhaust and possibly turn your muffler into a banana, Which is also what some of my friends managed to do.
How many miles are on the engine/injectors? Might not be a bad idea to send them in to be cleaned/tested.[/QUOTE
a little over 90k
How many miles are on the engine/injectors? Might not be a bad idea to send them in to be cleaned/tested.[/QUOTE
a little over 90k
05-01-2018, 01:26 PM
#18
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Both times I finally gave in and sent a set out to be cleaned the result was,, Oh yea,, its supposed to run like this!,, always a slap the forehead moment and why did I wait so long. 
05-01-2018, 09:37 PM
#19
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05-02-2018, 10:02 AM
#20
Right, that's not normal. The typical occurrence sounds like a fire cracker being thrown out the tail pipe.
If there is a detonation before the tail pipe, then there must be air and fuel being dumped into the exhaust. I would also check for exhaust leaks to make sure they aren't in play here. Otherwise, you could have some rich cylinders and lean cylinders.
If there is a detonation before the tail pipe, then there must be air and fuel being dumped into the exhaust. I would also check for exhaust leaks to make sure they aren't in play here. Otherwise, you could have some rich cylinders and lean cylinders.