backfiring

Well I finally got the car tuned today and got rid of the light throttle hesitation that has been plaguing me for ages. Now I have a new problem- at closed throttle, going down hills or just backing right off the car is popping and backfiring badly.

is it just a poor tune? or is there something else that could cause this?

Current AFR below and the old AFR in the attachment

Attachment 18364

sounds like its abit rich, backfiring is usually unburnt fuel in the exhaust, should ask your tuner

it sounds cool

Means that its running too rich under negative vacuum situations. Take it back to your tuner, there's a couple of parameters that can be changed to fix it.

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I thought that it would be caused by a rich condition, I was hoping that there would be something that i could do myself without having to take it back there.

just worried that it could damage the turbo, cat or muffler.

Did it happen during the tune at all? I'd take it back and complain

Check you overun fuel cut value.

Thanks Toda. This sounds exactly like my problem, if I press the accelerator even slightly the backfiring and popping stops.

just for those that are wondering what he is talking about-
Over-run fuel cut-off
The ECM implements over-run fuel cut-off when the engine speed is above 2000 rev/min with engine at normal operating temperature and the throttle position sensor in the closed position, i.e. the vehicle is "coasting" with the throttle pedal released. The ECM indexes the idle air control valve open slightly to increase the air flow through the engine to maintain a constant manifold depression to keep emissions low. Fuel is progressively reinstated as the throttle position sensor is opened.



I cant do this myself though right?
the really painful thing is, living in the hills, I am off-throttle all the way to the shop!

Quote:

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Originally Posted by mooshie

Thanks Toda. This sounds exactly like my problem, if I press the accelerator even slightly the backfiring and popping stops.

just for those that are wondering what he is talking about-
Over-run fuel cut-off
The ECM implements over-run fuel cut-off when the engine speed is above 2000 rev/min with engine at normal operating temperature and the throttle position sensor in the closed position, i.e. the vehicle is "coasting" with the throttle pedal released. The ECM indexes the idle air control valve open slightly to increase the air flow through the engine to maintain a constant manifold depression to keep emissions low. Fuel is progressively reinstated as the throttle position sensor is opened.



I cant do this myself though right?
the really painful thing is, living in the hills, I am off-throttle all the way to the shop!

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Was wondering what Adrian meant too, so thanks heaps for the information.

Subscribed to see how people fix issue

Quote:

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Originally Posted by mooshie

I cant do this myself though right?
the really painful thing is, living in the hills, I am off-throttle all the way to the shop!

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Maybe you can, what ECU is it?

it is an Autronic SM4

Quote:

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Originally Posted by mooshie

it is an Autronic SM4

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If the ECU isn't password protected, It's pretty straightforward.
Have you got the software?