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Old 10-24-2008, 04:17 PM   #11 (permalink)
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If you have have an OBD-I car, you need the appropriate Select Monitor to see for sure.

If you have a straight through or loud exhaust you can usually tell, the burble of the engine changes when the injectors are off or on.

I am under the impression that maybe besides some rare cars, that most should have some sort of fuel cut-off on deceleration. I have a SPFI engine in a 1989 Subaru GL that does the fuel cut off. In Subarus the fuel cut-off stops around 1750-2000 rpm from what I have seen. But even then, it is using less injector pulse width than in neutral. YMMV.

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Old 10-24-2008, 04:49 PM   #12 (permalink)
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Originally Posted by saunders1313 View Post
I don't have a scangauge. Is this the only way to tell, by feeling if the engine is trying to keep itself at idle rpms?
Try this...

While decelerating in gear (lets say ~2500rpm), turn the ignition off. If you feel the car instantly slow down faster, that could indicate that you're not getting a full cutoff.

On my car, the SG reads that .3gph are being injected while engine braking... But, with the engine off and ignition on, it also reads .3gph... BUT, while engine braking, I don't get any additional stopping force when I kill the ignition AND I feel the point at which fuel is reintroduced ~1400rpm in 5th. So, I know there's some fuel cut off - but I don't know if it's 100% or not.

Alternatively, you could tap into the one of the fuel injector wires and measure

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