Hi All


This is my first post so apologies if this has been asked before (searched a few recent posts but this query is different). I just bought a 2013 S Portfolio and I'm loving it :-) I am new to stop start and I'm gradually getting used to it, despite the initial annoyance


My question is twofold:


1. When I brake and come to a stop the engine stops. That's all fine but while keeping my foot on the brake I engage the handbrake. Once I remove my foot from the brake the engine starts again despite the fact that the handbrake is on. Is this normal? Seems a bit counter-intuitive to me, why not keep the engine off while the handbrake is on?


2. When the engine has stopped and my foot is on the brake - it will start the engine again after about 30 seconds even if I still have the brake pressed. Is this other systems requiring power or is my Jag acting strangely?


Thanks a lot!
Bob

 

That is typical of start/stop systems, Bob. The handbrake is independent from the process. When you stop you have your foot hard on the pedal and the sensor shuts off the engine unless you deactivate the start/stop with the button. I turn it off when I start the car as I find it annoying. If you don't hold down the brake pedal firmly when you are stopped it might not shut off either as I found with the BMWs.

 

Two thoughts. Firstly as yours is a 2013 XF this post should be in the X250 section (X260 is the new XF). Perhaps a mod can move it over to avoid confusion as the start stop system is different on the new model

As above the handbrake is independent - and I believe automatically disengages when you start to move the car.

The restart even if your foot is on the brake after some period of time is that yes - other systems require the engine running. E.g. The air con compressor so if you have the AC system on then when engine is stopped (e.g. At traffic lights) and the system is needed it has to start the engine up to run it

 

I read once.... unless my memory fails me.... that the only thing that will cause an early restart is the battery charge level. AC doesn't deteriorate enough to worry about but there's more going on electrically than we think about. Lights, audio, fans, heating, and some cars have a pump to keep the transmission fluid up to pressure.

 

From the Owners Manual:

The engine also restarts if one of the following occurs:

1. Intelligent stop/start is deactivated.
   
2. The vehicle's battery charge becomes low.
   
3. Demand from the Climate control system increases.
   
4. The vehicle's speed exceeds approximately 0.5 mph (1 km/h).
   
5. The accelerator pedal is pressed.
   
6. A shift paddle is used to select a gear.
   
7. Reverse (R) gear is selected.

The following conditions prevent an automatic engine stop:

1. Intelligent stop/start is deactivated.
   
2. The vehicle's battery charge is low.
   
3. The driver's seat belt is not fastened.
   
4. The external temperature is less than approximately 32°F (0°C).
   
5. The external temperature is more than approximately 104°F (40°C).
   
6. The engine has not reached its operating temperature.
   
7. Demand from the Climate control system requires the engine to be running, for example, when in Defrost mode.
   
8. A shift paddle has been used to select a gear.

 

As an aside, and not to muddy the waters... but for your information: with a manual gearbox the stop/start activates (subject to all the conditions above) when in neutral and with the footbrake on. However, it is possible to apply the EPB and then release the footbrake - the engine stays off. Engine will restart if either the clutch is pressed or the gear stick moved, however slightly.

 

I wonder if that includes AC activation or just heating/fans? I doubt it would include AC.

 

Compressor is running off of engine. So with the engine stopped it take the same amount of energy to run the fan through either hot radiator or cold coils. Naturally with time the radiator will get colder and the coils will heat up, but that's when the engine will kick back in

 

I follow but I'm saying it doesn't adjust to cabin temp during a temporary stop other than the fans. Rather it relies on the latent temperature of the coils to last long enough to either heat or cool (once at operating temps they should last longer than an average stop). If the fans don't have enough electricity then it starts, not because the temperature is wrong. I don't know for sure, just surmising from what I've read about stop/start although it could be implemented differently by manufacturer. Otherwise the start/stop would only activate if the cabin temperature was within a set range and that's not how they work. I have read of people complaining that lots of start/stop activity noticeably affects cabin cooling.