Deceleration Fuel Cut-Off Rpms Too High Galaxy 2.3, 2.0

[Z42]

My 1998 Galaxy 2.3 MK1 cuts off fuel injection while driving downhill at about 3600 RPM and resumes it at about 3500 RPM. What are the normal RPMs for that and if this is by design, what was the reason Ford engineers decided cut-off RPMs must be so high?

 

There is no doubt about it, I first felt it then checked injection times through OBD and trough the LPG controller. I asked qualified mechanics to double check - they confirmed it was so.

I've checked several 2.3 and 2.0 MK1 Galaxy either myself or by asking their owners to do that and all of them behaved the same way.

I also had my car checked multiple times in many repair shops including the local official one. No possible reason was found. I also regularly monitor fuel trims by myself, LTFT usually resides between 0 and 8% (on petrol and LPG).

 

I found a hack to work it around when I need better engine braking but it is not very convenient to be used often. When the VSS sensor is disconnected, the ECU loweres cut-off threshold to about 2600 RPM (resumes injection at about 2500 RPM) which is much better although I'd prefer it was 1500.

 

I'm missing the engine braking so much that I even consider adding an external cut-off trigger but my wife doesn't believe it can be by design and insists we must have our car fixed instead. So without trustworthy data from a reliable source I am blocked from doing anything but just disconnecting VSS connector when necessary...

[BrianH]

The clutch on the 2.0 isn't particually big - I'd suspect you'd shorten its life somewhat by using it to assist with engine braking anyway.

 

Don't know of the reasoning for it - I know the Focus i've got does the same thing with cutting injector pulses on overrun though offhand don't know the rev range it does it at.

 

Only thing i can see you could do is investigate remapping to see if it can be altered, though would expect you to gain engine braking with no fuel going in anyway?