Hi, I have a 2019 R-Dynamic with about 15k miles. I've taken very good care of it, and haven't had many issues until recently.
Note - I leanred to drive on a manual transmission at 13, and every car I've had for the last 30 years has been manual - so I'm pretty sure the issue is not user error.

Essentially, the engine loses power in this circumstance: when I am coasting in neutral (such as to stop at a light or stop sign), the moment I push in the clutch and shift into either first or second gear. This exclusively happens at very low speeds, and never when stopped. Typically, I notice it right away and pull the gearshift back into neutral, and about half the time the engine actually starts back up, and the other half of the time it remains dead and I have to come to a full stop and restart the car normally. But, pretty often I don't even notice (as when I'm stopping at a red light, and shift into 1st right before I come to a full stop). The car doesn't even really indicate that I've lost power, I just end up trying to go when it turns green and nothing happens.

It isn't stalling out - the RPMs drop steadily to zero from idle under the above circumstances.

I had it at a local Jaguar dealer and they didn't find any issues (but at that time I hadn't narrowed down precisely when it was occuring, and because they just drove it on the highway to diagnose it, they didn't see any problems). I wo;uld like to take it back in now that I can show them what is happening, but I would LOVE any theories anyone may have to help them diagnose it properly.

Also, it may or may not be related, but when stopped and in neutral, there is a drop of about 2,000 RPMs from idle whenever I push on the brake (so it goes from just over 5k to just over 3k, I think). This seems way high and I hadn't noticed this until now, though it may be normal?

Edit: forgot to mention that I do have VelocityAP tune and pulley, and I suppose it could be related but the problems did not start until about a year after I installed the VAP tune, so it seems unlikely. I also have the short throw shifter, but I cn't imagine that is related. No other mods

Any ideas?

 

Can you hook up an OBD2 tool and get real time measurements when it happens, especially fuel pump pressure? Any codes?

My first thought is loose connector to your fuel pump.

@scm can you advise as this happened to you:

https://www.jaguarforums.com/forum/f...issues-268113/

Bring it back to the dealer and drive the tech yourself to show them how and when it happens.

 

No codes, and I haven't noticed anything out of the ordinary when checking my OBD2 tool.

 

Doesn't sound like mine at all - mine would stutter when I opened the throttle, and I got codes relating to the high pressure fuel rail. MIne's not a manual, either.

Hope the OP gets to the bottom of it and can get it sorted out.

 

I know it sounds improbable, but many threads here with odd electrical related issues have to do with dying batteries. These cars are very sensitive to battery output. You have a 2019, so that would make the battery 5 years old. There are some owners here who have batteries that last longer than this, but for the most part AGMs only last this long. Perhaps get a new battery (yeah, I know, pricey) and see if that helps. There are all kinds of threads here about replacing the batteries and doing all the dance steps for the windows.

https://www.jaguarforums.com/forum/f...myself-208222/

 

Possibly a crazy idea, but have tried disconnecting the Start/Stop function (in case there is some malfunction there)?

 

"Also, it may or may not be related, but when stopped and in neutral, there is a drop of about 2,000 RPMs from idle whenever I push on the brake (so it goes from just over 5k to just over 3k, I think)."

Your car idles at 5K? Typo?

 

Oops, yes, remove a zero

 

I was having battery issues, but that was resolved when I took it to the dealership two months ago. They replaced the battery.

 

hmm, I disengaged it with the button but didn't try disconnecting it. Maybe worth a shot

 

Yep, that was my first thought - the stop/start system is playing up.

 

+1
I'd bring it up with the tuner as they may have some ideas. I still don't get the RPM drop that the OP mentioned.

As for putting in neutral before stopping, I used to do that a long time ago. Have you tried to hold it in gear, tap the gas, down shift to 2nd and bring it to a stop with the brake instead to see what happens?

 

I can and usually do downshift. If i leave it in second, disengage the clutch and shift right into first to stop (with the clutch still disengaged obviously), it's fine. But if I keep the shifter in the neutral position for a few feet as I roll to a stop, the power loss occurs the moment I move the shifter into 1st while the clutch remains disengaged.

Having narrowed down when it happens precisely, I can avoid it - but obviously I want to figure out what the issue is regardless.

 

Wonder if @HermanWiegman could chime in and give his thoughts considering his vast knowledge of the 6MT?

 

Yes, he and and our other MT gurus @lizzardo and @Unhingd!

Also @Stuart@VelocityAP or Chris may be able to rule out the modified ECU's role in this.

 

Thanks to @JagCode3, this thread was just brought to my attention.
1. My first thought, as others have mentioned, is an issue with the stop/start function. When you say "power loss" , do you mean reduced power or the engine shuts off?
2. Even if you meant idle falls from 500 rpm to 300 rpm, that's all wrong as well. Idle should be around 700 rpm. I suspect an issue with the idle control valve, or the idle control valve sensor.

Your best bet will be to ride (or drive) with the mechanic to demonstrate the issue. I have had to do that on a clutch and a steering rack issue that they could not recreate during their routine test drive..

 

I too have been drawn to this thread. I had, once or twice in early ownership, the start/stop system get confused in a stop and go situation. That was indistinguishable to an outside observer from a rookie on the clutch stalling the car. I now routinely turn it off as part of my startup sequence and only turn it on when I'll see benefit from it. I just don't have long traffic lights as part of my daily life any more.

My version of "Atomic batteries to power, turbines to speed, ready to move out" is routine now:

- Start
- Seat belt
- Start/stop off
- Dynamic mode on
- TracDSC
- Wait for engine to come off fast idle
- Proceed

As Lance points out, if you can reproduce it, having your mechanic see it happen will be beneficial, even if it's "See, I'm not crazy." I had to do that with my clutch. It was intermittent, depending on where the broken pieces happened to be either wedged or floating at the time.

 

@blthomas Can you let us know the outcome?

 

Paging @Onca Engineering @HermanWiegman - any ideas on this unique problem? Still waiting to hear the outcome from @blthomas

 

@JagCode3 and @WSHudds thanks for the call in. I've been busy with the YouTube channel, and videos on the Y-pipe upgrade.

@blthomas Your car's poor idle behavior when coming to a stop and coinciding with shifting into gear is odd... especially for a 15k mile example.
Here is what flows from my engineering mindset.

1. weak idle usually comes from ...
   a) restricted air flow, (but you said you car feels "normal" at highway speeds, so probably not your car's issue)
   b) poor airflow throttling, (the electronically actuated throttle body does develop some sticking with age or non-use, some cleaning could be in order)
   c) low fuel delivery ( usually in a DI engine, there is plenty of fuel delivery authority ... probably not your car's issue, but the VAP tune may be suspect at idle)
   d) poor ignition timing (probably not the issue here)
2. a linear drop in engine RPM comes from ...
   a) loading on the engine/flywheel, (is your clutch sticking? or is the Throw Out bearing sticking?)
   b) a collapsed throttle position, (if there is insufficient air flow to support idle, then RPM's drop linearly to zero)
   c) collapse in fuel delivery, (probably not your issue).
   d) loss of spark (resulting in a rapid drop)

I am glad to hear others suggesting a battery health check... your car has a new battery now.
Other ideas around Start/Stop were rational and easy to try...

But if you feel the clutch is "smooth" and not loading the engine excessively... then I'd vote for an inspection of the air intake system, from filters, to throttle body.
My throttle body had some fowling from the PCV system, which I cleaned up... could be your car's issue.
I doubt your SuperCharger Bypass valve has any bearing here, at idle... and a dysfunctional one would probably throw a code.
Lastly, what fuel grade do you fill your tank with?
At only 15kmiles and low usage, your car's fuel injectors may be starting to clog or "dribble" gas in stead of atomizing it at idle.

Drive well,
Herman Wiegman
Onca Engineering