1993 Subaru Impreza Logo
C
Clement Posted on Dec 14, 2014
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Misfire/Backfire and not accelerating properly wondering whats the problem?

I was driving on a broken exaust right where my rear cat was and the fixed it (weld) then it start to not accelerate properly and then I found out that my air filter was kind of open it wasn't sealed properly so I sealed it meanwhile I have never changed my filter so maybe that's a problem? I also was revving the engine and I keep hearing this popping noise as soon as I press the pedal not all the time but occasionally. I went under the hood and found out that the popping noise sounds like its coming from air filter cabin anyone have any ideas on whats goin wrong with the car?

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Kevin Blair

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  • Posted on Dec 15, 2014
Kevin Blair
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1st get a new air filter I recommend a quality brand like the oem one or purolator.
2nd remove and clean the maf sensor. Start with the screw clamp on the intake hose. Then unplug the sensor just squeeze the tab and wiggle it off. Now remove the 4 - 10mm boltsthat hold the maf sensor on the air box. Use caution as some models have a housing with brackets that are loose when the above 4 bolts are removed.
Next clean the air flow sensor using crc maf cleaner or other maf sensor safe cleaner. This is necessary as the sensor gets dirty as the miles accumulate. Make sure the sensor wires are very clean and let it fry for 30 mins before re-installing the sensor.

I would inspect the blower motor for debris as a 93 impreza doesn't have a cabin filter.
You can access the hvac fan from under the glove box see the attached video for how to. I know its not the correct subaru but the procedure is the same. Misfire/Backfire and not accelerating properly won - misfire-backfire-not-accelerating-tq5sh21jzhkdedjt044n20r3-4-0.jpg

Testimonial: "i did tjis problem still occurring when im on the highway trying to quickly make it to work on time the rpm needle has problem getting me to the destination quick enough. what I mean is the rpm needle jumps up and down even tho my foot is holding steady pressure on the accelerator if I decide to give it a little more pressure it starts to make a popping noise sounds like its coming from cabin very confusing could it be from my throttle body?? throttle positioning sensor ?maybe"

jolly

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  • Posted on Dec 15, 2014
jolly
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Check cam shaft timing, park plugs, HT leads. If all okay, backfiring is a sign of a lean mixture, can be the MAF sensor or low fuel pressure, fuel pump problems are very common, but also a MAF sensor broken contact.

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  • Posted on Dec 15, 2014
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Air filter not sealed and never replaced, you should clean the MAF sensor since the dirt passes through the air filter.

Testimonial: "i did tjis problem still occurring when im on the highway trying to quickly make it to work on time the rpm needle has problem getting me to the destination quick enough. what I mean is the rpm needle jumps up and down even tho my foot is holding steady pressure on the accelerator if I decide to give it a little more pressure it starts to make a popping noise sounds like its coming from cabin very confusing could it be from my throttle body?? throttle positioning sensor ?maybe"

AwdSyco Subaru

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  • Posted on Jan 30, 2015
AwdSyco Subaru
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You should spray with MAF/TB cleaner to clean throttle body(TB) too. While you're there, spray the IACV Intake Assist Control Valve. If your RPM fluctuates, most likely the carbon build up block the air to assist idling when engine is COLD. IACV is located at front/top of throttle body. If you found carbon dust build up in IACV, you solve your issue.

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