[arpandiv]

does this occur when you step off the accelerator ?

[amit_mechengg]

Originally Posted by arpandiv

does this occur when you step off the accelerator ?

yes when in city i accelerate and then when i put my feet off the accelerator then i hear this sound. i dont hear this while accelerating.

[bigdad]

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[Blue Thunder]

looks like engine tune-up needs to be done : this is probably the sound of the engine backfiring.

[amit_mechengg]

Originally Posted by Blue Thunder

looks like engine tune-up needs to be done : this is probably the sound of the engine backfiring.

do u mean to say misfiring? mine is alto 800 cc MPFI engine, i doubt there is much scope of tuning in this!!

[arpandiv]

have you got engine de-carb ?
I hope its not a leaky exhaust valve.

[alpha1]

Leak in exhaust pipe.

[gd1418]

get the injectors cleaned buddy..

Originally Posted by amit_mechengg

do u mean to say misfiring? mine is alto 800 cc MPFI engine, i doubt there is much scope of tuning in this!!

[amit_mechengg]

is it that my exhaust is blocked, because the same thing had happened with my bike and the silencer had got clogged. do i need exhaust cleaning?

[dadu]

Originally Posted by amit_mechengg

is it that my exhaust is blocked, because the same thing had happened with my bike and the silencer had got clogged. do i need exhaust cleaning?

Most probably a ruptured joint in the exhaust, put it on a ramp and check.

[adman77]

The same thing happened with my car after I got a FFE. Changed the FFE thrice after that, but the sound remains.

[Blue Thunder]

Originally Posted by Blue Thunder

looks like engine tune-up needs to be done : this is probably the sound of the engine backfiring.

Originally Posted by amit_mechengg

do u mean to say misfiring? mine is alto 800 cc MPFI engine, i doubt there is much scope of tuning in this!!

There is the possibility of misfiring even in the case of MPFI engines with ECU : as long as it is spark ignited, this possibility exists. There could be something wrong in the ECU, which could be sending the charge at the wrong time to the sparkplugs.

I am giving this as a likely cause, since you have mentioned it happens only while decelerating , and not all the time.

Anyway, time to get it examined at a good garage, since continued running in this condition will deteriorate the engine in the long run.

[veyron1]

Shan2nu's right. That "misfire" is technically due to an overtly rich/lean mixture/AFR at zero throttle.

@Cyrus43: Technically, the engine is never "zero-fuelled". Even at zero-throttle, the engine receives enough fuel to idle. Although the TB is at zero degrees, IACV supplies minimal air and the injectors (or in this case, carb), fuel. When that fuel does not receive enough air to supplement it's combustion, unusual combustion such as this "popping" happens.

This phenomenon is far more apparent in carbs, giving the impression of "tuned FI's".

@sumeet: Check your idle solenoid.. get your carb serviced, and replace the primary jet & primary & secondary needles, if necessary.

[amit_mechengg]

Originally Posted by veyron1

@sumeet: Check your idle solenoid.. get your carb serviced, and replace the primary jet & primary & secondary needles, if necessary.

ya my idle solenoid is having problems currently as the throttle body is clogged due to K&N filter passing on dirt in it. while idling the rpm fluctuates.
so it is due to this i am facing the exhaust problem?

[rdkarthik]

Originally Posted by veyron1

@Cyrus43: Technically, the engine is never "zero-fuelled". Even at zero-throttle, the engine receives enough fuel to idle. Although the TB is at zero degrees, IACV supplies minimal air and the injectors (or in this case, carb), fuel. When that fuel does not receive enough air to supplement it's combustion, unusual combustion such as this "popping" happens.

No. Conditions at zero throttle and RPMs above a certain limit (~2000) will enable a fuel-cut operation to cut emissions and increase FE. All modern day cars have this feature.