So Question is; On fuel injection engines when in gear, and the throttle is fully closed (E.g. under engine braking) is there any fuel being injected into the engine?

I know more modern cars don't, but was just wondering about the older type felicia.

Cheers

Yes and no...

it depends on a few operating conditions.. Vacuum measure at the map sensor, and rpm, there is a preset level for both at which the fueling cuts off, typically speaking it is around 1500rpm on most ecu's but it does vary, so for example if you are doing 5000rpm and you lift off, the idle switch in the throttle body closes which tell the ecu the throttle is shut fueling is cut off, then when the rpm drops below 1500rpm is switches back on again, and there is a similar logic for the vacuum level too. Also as a side note to this it retards the igniton timing when it's under heavy vacuum too, in this condition if the fueling stayed on then you would get lots of pops and bangs and possibly backfires in the exhuast system which could melt the catalytic convertor.

hope this helps.

Yes, it certainly does, might aswell mark this topic as solved

Posted and solved within 10mins, nearly as fast as the felly

Of cause if someone else wants to add anything, they can.

Thanks

Edited 31 March, 201412 yr by R_U_AFA

Also as a side note to this it retards the igniton timing when it's under heavy vacuum too, in this condition if the fueling stayed on then you would get lots of pops and bangs and possibly backfires in the exhuast system which could melt the catalytic convertor.

I don't quite understand this part. You said that an off-throttle condition under engine braking cuts the fueling IF (heavy vacuum AND rpm > 1500) which is true, Felicia included. So why the need for a retarded timing too if the fueling is off?