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Discussion Starter · #1 ·
I have a bone stock wrx except for the airbox removed with just over 15k miles. Every once in a while I will be starting from a stop and when I give the car gas I get a little backfire. It is not very loud but this has happed at least a half dozen times now. I would take it to the dealer, but there is no way I can duplicate this.

Has anyone experienced this problem? Is the car loading up with fuel? What should I do?:confused:

Thanks
 

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hmmm, i havent experienced this for sure, and i havent heard about this from anyone else....does it do it when your giving it gas...or when the revs are coming down? Does it do it in neutral or when your in gear? Fill us in and im sure dan or jim or someone could help you out with the technical aspect of why this is happening....i mean when my revs are coming down in neutral ill get some popping...is this what your talking about?
 

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Use the term 'after-firing', which refers to unburnt fuel igniting in your exhaust system. A back-fire is when a flame front moves back through the induction system, which can be a dangerous situation. On the WRX a back-fire will (and has in at least one case) destroy the intercooler and may damage the compressor. It's loud, too.

-Pace
 

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Discussion Starter · #4 ·
I am not sure if it is a back-fire or slight detonation. From what I have noticed it only happens either when I am in neutral and give it gas or start to leave from a start (at the point when you give gas and start letting out the clutch). It never happens coming of of high RPM's.

The noise is like a little poof (very slight), and it is NOT the BOV. Remember it only happens either in idle or leaving a stop light (no boost for BOV to activate).

I always use 91 octane (CA, 91 is the highest). Maybe I am getting bad gas. 95% of the time I use shell because of the gas card I have. I sometime go to a no name station because of the 12 cents difference in price.

Thanks for all the helo.
 

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this happens to me occasionally on start up from a stop, usually at about 1800 rpm its like a little pop of hesitation maybe lasts <1 sec. it doesn't make a very loud noise though.
 

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HIGHBOOST said:
I am not sure if it is a back-fire or slight detonation. From what I have noticed it only happens either when I am in neutral and give it gas or start to leave from a start (at the point when you give gas and start letting out the clutch). It never happens coming of of high RPM's.

The noise is like a little poof (very slight), and it is NOT the BOV. Remember it only happens either in idle or leaving a stop light (no boost for BOV to activate).

I always use 91 octane (CA, 91 is the highest). Maybe I am getting bad gas. 95% of the time I use shell because of the gas card I have. I sometime go to a no name station because of the 12 cents difference in price.

Thanks for all the helo.
I personally don't trust "no name" gas stations. I don't care how much cheaper the gas is. The risk/reward relationship just isn't there.

You could check if it is bad gas by putting in an octane booster or toluene/xylene. Make sure the octane booster has MMT. The alcohol octane boosters do almost nothing. A gallon of toluene or xylene (available at paint or home improvement stores) will also raise the octane. IIRC, toluene and xylene have an octane rating of approximately 116. So, if you put one gallone in a tank with 9 gallons of 87 octane, you would raise the octane in the tank by about 3 points (to around 90).

Predetonation usually happens under very high engine loads though. This really doesn't sound like predetonation because you will likely be under very low boost when you are hearing the noise.

If better gas doesn't get rid of the problem, take it to the dealer. At least he can check to try to find something.

Rich
 

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speaking of no name gas, you'd be surprized at the what brand of gas you are getting at any gas station, most share national pipelines and share time in the pipes they don't use "pigs" in the pipelines any more so all of the gas that travels through them is mixed with the gas that went through before it. the grades are separated but the brands can mix, so you could be buying texaco gas at an amoco, or speedway gas at a citgo, etc. Granted it is only a portion of the both that mix but The only time you can be sure that you're getting what you paid for is if you know the company has a dedicated system. Like Chevron, for example, however only about 3% of gas companies have dedicated systems.
 

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02WRX82 said:
speaking of no name gas, you'd be surprized at the what brand of gas you are getting at any gas station, most share national pipelines and share time in the pipes they don't use "pigs" in the pipelines any more so all of the gas that travels through them is mixed with the gas that went through before it. the grades are separated but the brands can mix, so you could be buying texaco gas at an amoco, or speedway gas at a citgo, etc. Granted it is only a portion of the both that mix but The only time you can be sure that you're getting what you paid for is if you know the company has a dedicated system. Like Chevron, for example, however only about 3% of gas companies have dedicated systems.
I'm looking at this from a different perspective. I assume (or hope) that a name brand such as Amoco has better standards or quality control such that when I pay for premium, I actually get premium in my tank.

Rich
 

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that's exactly what the companies want you to believe. To elaborate on my last post, the amount of gas that mixes in a pipeline is i believe 15-25 feet of the gas in the pipes which can be anywhere from 12" - 40" in diameter. so the mixture can vary quite a bit between brands. and like i said only about 3% of gas companies have their own dedicated system. i know chevron does but i'm not sure about amoco. I still refuse to put anything but amoco or chevron gas in my car though, because i have gotten bad gas at other places and never at amoco.
 

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02WRX82 said:
that's exactly what the companies want you to believe. To elaborate on my last post, the amount of gas that mixes in a pipeline is i believe 15-25 feet of the gas in the pipes which can be anywhere from 12" - 40" in diameter. so the mixture can vary quite a bit between brands. and like i said only about 3% of gas companies have their own dedicated system. i know chevron does but i'm not sure about amoco. I still refuse to put anything but amoco or chevron gas in my car though, because i have gotten bad gas at other places and never at amoco.
You're not following the concern that I mentioned earlier. I have more confidence that brand name gas stations will actually put premium gas into the well that pumps premium gas. I could be wrong but my fear is that a no name gas station owner would deliberately put low octane gas into the high octane gas well. It has nothing to do with the pipelines. It has to do with the honesty of the gas station owner and the hope that in a name brand gas station that there is some sort of quality testing to make sure that a gas station owner isn't destroying the Amoco (or Exxon, Mobil, Texaco, etc.) name by selling 87 octane gas as 93 octane gas.
 

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oh, yea i mis understood. i definetly trust amoco and other top names to have the correct grade in each pump.
 

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The quality of the gasoline at any one gas station has a lot to do with the volume of traffic that they see. Gasoline does stale, and the small no-name stations may have the gasoline sitting in their tanks for a long period of time.

-Pace
 

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Well, this topic strayed...... BACK ON TRACK.

If this is during acceleration you are probably misfiring. Check you spark plugs and make sure they haven't fouled. This shouldn't happen when you are accelerating. detontaion or ping (whatever your preference of term is) don't make a puff sound, or a pop sound like a back fire. They make a metalic "ping" hence the term ping. This is bad, much worswe than a misfire. If you plugs are fouled clean them or get new plugs.

If you look at the plug and the electrode that hangs underneath the plug itself is melted away then you have been running under a lean condition in that cylinder and you should have that checked out. (THIS IS A REALLY BAD THING!)

If nothing is wrong with your plugs then check your sires. if they are ok, then check the ignition system. If you still can't find anything wrong then get an OBD-II reader from someone and drive around with it one for a few days. When you hear the back fire then save the info fromt he previous minute or so and have someone who knows what they are talking about read it.
 

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my car has almost made alittle "puff" sound when you let off othe gas or when you shift. Especially after I got my Stage II TurboXS kit, I can really hear it. If I am just standing still and I rev it a little, it sounds all normal reving up, on the way back down it goes "blub blub blub blub, poof" Not realy loud or anything just makes a nice poof hehe. Im thinking its just running a little rich as it always did. Its probably just because our cars like to run so freakin pig rich! 10:1 a/f ratios are the richest ive ever even seen
.
 

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It's because when you shut down the engine real quickly the car continues to put gas into the cylinder, but it just doesn't ignite it. When the gas reaches you cat (which is REALLY hot) it ignites and bucause of the stock muffs you only hear a puff as opposed to the popping you would hear on a V8 with an aftermarket exhaust.

The car running rich is to protect you against detonation from the turbos. It's a safety thing. The extra oxygen forced into the cylinders will bind with womething hot and cause it to burn, so you want it to be fuel and NOT your cylinder wall or piston. Also, any unburnt fuel acts as a coolant for the cylinder walls.

get an aftermarket exhaust (just please please please don't get a fart can) and the backfire will sound a lot louder and more enjoyable.
 

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Ya it sounds kinda kewl with my 3"turbo back. It reminds me of the rally cars!
 

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HIGHBOOST said:
I have a bone stock wrx except for the airbox removed with just over 15k miles. Every once in a while I will be starting from a stop and when I give the car gas I get a little backfire. It is not very loud but this has happed at least a half dozen times now. I would take it to the dealer, but there is no way I can duplicate this.

Has anyone experienced this problem? Is the car loading up with fuel? What should I do?:confused:

Thanks
I get what you are exactly describing too. I was curious, did you find out what the problem was? Because I've gotten that at times to, very randomly however. It feels like a pop in the exhaust or what not, but I can feel it through the accelerator pedal.
 

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It has happened to me both stock and with mods. it is very likely unspent gas in the exhaust getting ignited post-turbo. If you smell gas when this happens or it mainly happens whenengine is not yet warmed fully, may be a malfunctioning tumble valve ( happened to me) whose purpose can be to enrichen the mixture. Got it fixed, "back fire" happens alot less
But it still happens............these cars run very rich---check the soot in your exhaust for proof.
 

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HIGHBOOST said:
I always use 91 octane (CA, 91 is the highest). Maybe I am getting bad gas. 95% of the time I use shell because of the gas card I have. I sometime go to a no name station because of the 12 cents difference in price.

Thanks for all the helo.
You got a tank of bad gas. Add some water remover or octane boost and start buying your fuel elsewhere.

-Jim
 
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