strange XJL / eco behavior
 

I had a few (2-3?) strange experiences driving my XLJ last week, that made me question if I was imagining things.

When I drove the car after the wife took it out the day prior, the car suddenly shut of the engine at stops. I previously had never recalled this behavior, honestly, but found the eco mode on/off button and tested it, and turning it off stops this behavior. Today / yesterday I took it out, and drove it around, and of course eco mode is on by default, but the car does not shut off the engine at stops any more. Why would the engine start / stop randomly work? Could it be detecting the battery is low and staying on to charge it?

Also, 2-3 times this past week, when I came to a stop at home or store, and I turned the knob from "Drive" to "Park", the engine turned off. I went to shut off the engine by pressing the Power button, and it restarted the car. I was really confused until the 2nd / 3rd time I saw it happening again. Again I drove it yesterday / today, and now it does not happen, I have to press the Power button to turn off the car.

These random events made me question if I was imagining things. Anyone else experienced this or have any insight into what may be causing this?

Having the eco only work occasionally is a classic sign of a tired battery. How old is yours?

Thanks! It's about 2 years old I think, although the car was not driven often, but was on a battery tender much of that time when not driven. Perhaps the battery tender is not working as well as expected.

How about the auxiliary battery?

There is a list of tings that all have to happen before start/stop will operate. If one thing isnt completely warmed up or charged, the system will not work. Its more complex than one little thing.

Just remove the negative cable from the AUX battery and you will NEVER have to be irritated with this useless feature again. Best mod ever!

TJ

I think you are experiencing a normal working eco mode that performs and shuts off the engine when about a dozen conditions are met for it to say okay do it. Prior to your one day of strange behavior there were some required conditions of the eco system that were not met and it did not shut off the engine. Now that your eco system's inhibits are not coming on and the car is running perfect, the stop/start is enabled more.
Here is a list of all the inhibits that at any one time preclude the stop/start function from coming on. One or more must have been happening previously. My opinion.

•  
  • Auto stop/start off switch has been operated by driver
  • Transmission not in neutral
  • Hood open detected
  • Driver door detected open
  • Driver seatbelt not fastened
  • All terrain progress control special programme selected
  • Climate control demand exceeds calibrated threshold
  • Heated windshield operating
  • Trailer connected
  • Brake booster vacuum below threshold
  • Engine coolant temperature below threshold
  • Engine oil temperature below threshold
  • Battery state of charge low
  • Battery cold cranking capability below threshold
  • Ambient temperature above 40°C
  • Ambient temperature below 0 degree C

2011 XJ, the glove box lid will flop open overnight if battery gets low, I now put it on a real battery charger to bring it back to 100% It was a mystery until I realized 8 mile drive daily was not enough.

Jaguardeseo, I suggest purchasing a high quality battery maintainer/charger like you see discussed in many of these threads and recommended on the Forum. I use the CTEK MXS 5.0. This quality maintainer/charger will keep your AGM battery up to where is belongs. The CTEK kits come complete with a "pig tail" to permanently install and have a convenient quick connector to hook up the CTEK charger when you come home.

For details of how I installed my CTEK, including photos, see: https://www.jaguarforums.com/forum/x...lation-130801/

Note that the negative pigtail lead must be connected to a chassis ground, and not directly to the battery negative terminal.

You could be on the right track, Freddy! I've had Ford and various Japanese cars (family) where the stop/start does not happen every time the vehicle comes to a stop. Various scenarios have to be met before it activates and shuts off the motor....

A favourite one is the climate control outside of parameters. If your AC isn't working well the Eco start / stop won't work, because the AC could be putting too much load on the electrical system.
I recently got my AC topped up and the Eco start / stop is much more eager to spring into action.

Just disable the stupid system as part of your "car on" procedure, every time. It is a very poorly implemented system and never works, indeed it needs like 14 parameters to be met to activate. Battery weak at all? Nope. Car cold? Nope. Car hot? Nope.

Just disable it and save yourself the headache.

So glad I read this link.
I bought a 2016 XJL
six months ago. The stop start function came on just a few times when I initially got the car.
Then I noticed it never came on after that.
Last weekend I was coming home from a long road trip and it started the stop start function again!
I couldn’t figure out what was going on and I thought something might be wrong with my car.
sounds like that is not necessarily the case.

I definitely would like to have that thing turned off permanently. I find it very annoying

If the eco start / stop is not working consistently, then it means something is likely to be wrong with your car, e.g. low battery, A/C not working efficiently.
Once your car is warmed up the start / stop should cut in every time you apply the brake firmly when you are at a stop.

I don't understand why people don't like it. It's very easy to control. A light press on the brake pedal will hold the car still, with the engine running. A firmer press on the brake pedal will trigger the eco start / stop. I find it very useful in traffic and can choose whether to trigger it or not simply by how much pressure I apply to the brake pedal.

As a Jag and long time Alfa owner, feeling my big V8 suddenly die gives me a little heart attack every time it kicked on. Also, it does not start up fast enough for my liking (not 48v), and just puts extra strain on everything for absolutely no gain at all. So with my tune, I permanently disabled it. I am very, very happy now.

Mine is the 3.0 Diesel, so minimising pollution is a good idea (so I can offset my supercharged V8 XKR usage :icon_biggrin:), and it starts up pretty quickly especially if I lift my foot a little earlier in anticipation.

After disabling the eco stop/start, I thought I'd provide the convenience of reconnecting the small battery ground by installing a switch at the cable connection incase I wanted to enable the function ever again.

https://cimg8.ibsrv.net/gimg/www.jag...e2dd762a10.jpg

Nice addition!