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Injectors shut off during deceleration

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Injectors shut off during deceleration

Postby MMamdouh » Thu Jun 27, 2013 12:55 pm

I know that the injectors are shutoff by the ECU during deceleration on some engines but was wondering if this is the case with our Daewoos...

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Re: Injectors shut off during deceleration

Postby Rodd1s » Thu Jun 27, 2013 2:06 pm

Doubtful. They are based on rather old EFI technology before such ideas were put into effect (around 2005-ish I think), plus they'd be a lot more economical if that was the case.

I'm sure such circuitry could be implemented to adapt an engine to perform in such a manner with some basic logic, i.e.: IF no throttle AND engine speed > ~2000rpm = cut injector signal.

Obviously you'd need to tap some signal wires that feed the ECU, which might mess them up - so maybe adding your own sensors to monitor throttle position and engine speed, then adding some sort of relay/impeded-bypass circuit to the signal wire of each injector to cut or enable their flow.

Just a thought.
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Re: Injectors shut off during deceleration

Postby Daniel » Thu Jun 27, 2013 4:19 pm

MMamdouh wrote:I know that the injectors are shutoff by the ECU during deceleration on some engines but was wondering if this is the case with our Daewoos...

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This is described at end of engine controls section 1F-314.
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Re: Injectors shut off during deceleration

Postby exist3nce » Thu Jun 27, 2013 6:39 pm

I know my 2004 Optra has this for a fact. Around here we call it decel fuel cut.
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Re: Injectors shut off during deceleration

Postby benzino » Fri Jun 28, 2013 3:43 am

yeah my lanos does it.

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Re: Injectors shut off during deceleration

Postby Rodd1s » Fri Jun 28, 2013 1:33 pm

I doubt mine did it, mainly judged by the 'over run' made audible by the exhaust when the centre silencer was removed... still popping and banging for several seconds after coming off the throttle as unburnt fuel gets chucked down the exhaust.

Search youtube for "rev 'n rumble", watch the first result (should be a frame of the tail end of a Lanos, my old Lanos) to get an idea of what kind of popping it made all the time.
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Re: Injectors shut off during deceleration

Postby benzino » Sun Jun 30, 2013 4:30 am

it only does it over a certain speed/rpm to maintain smoothness
i.e coasting in 5th on the highway or coasting down a hill in a gear that maintains as much speed
if it did it at low speeds/rpm, it would be very jerky

guarantee your's did it Rodd but unless you have some sort of indicator, you would never know
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Re: Injectors shut off during deceleration

Postby Davinci_360 » Wed Jul 03, 2013 7:24 am

I once used a LED test light on the fuel injector circuit to diagnose an intermittent fuel delivery issue with my Lemans. It had TBI, not MPFI, and it DID have fuel cut off during deceleration. If it was around back then, I'd assume it's still implemented in the more modern Daewoos.
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Re: Injectors shut off during deceleration

Postby Trey05Woo » Sat Aug 10, 2013 1:55 pm

Truth be told every OBDII system cuts off fuel during deceleration. This is mostly done to reduce emissions, and protect the catalyst. Every OBD II vehicle since 1996 (in the US anyway) has this feature. Modern systems are just much more precise and can regulate fuel feed based on more variables now.

You can run the test yourself:

Remove the passenger seat, back probe any injector trigger wire with a test light, coast the vehicle while applying the brakes, you will notice the test light stays off.
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