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Discussion Starter · #1 ·
For the past few weeks now I've noticed my car will sometimes do a slight "lurch", a few seconds after coming to a complete stop but staying in D and holding the brake pedal down, e.g. at traffic lights. Also, the engine RPM will seem to fluctuate a little bit on a steady throttle pedal position at low speeds in low gears (although I think that's mostly just after cold start) and I sometimes feel a small surge on upshift from 2nd-3rd. Transmission fluid and filter pan was changed about 3 years and 10,000 miles ago.

I guess I'm probably also looking at a visit to a ZF specialist?
 

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I feel your pain!

I hope it is just software related.

For the past few weeks now I've noticed my car will sometimes do a slight "lurch", a few seconds after coming to a complete stop but staying in D and holding the brake pedal down, e.g. at traffic lights. Also, the engine RPM will seem to fluctuate a little bit on a steady throttle pedal position at low speeds in low gears (although I think that's mostly just after cold start) and I sometimes feel a small surge on upshift from 2nd-3rd. Transmission fluid and filter pan was changed about 3 years and 10,000 miles ago.

I guess I'm probably also looking at a visit to a ZF specialist?
 

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Trying to think about this logically, the engine is idling and you are in gear, so what would make the car lurch a little? I'd check for fault codes for a TPS or possibly a MAS which is causing your engine to increase revs momentarily.....
 

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Discussion Starter · #4 ·
I'll check for fault codes when I get a chance this week. If by MAS you mean Mass Airflow Sensors then I changed both of them a couple of months ago. Regarding the lurch in gear at standstill I guess that could be a few things but amongst those might be a problem with one of the valve solenoids in the transmission. I guess it could also be something brake-related, like momentary loss of brake pressure.
 

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I'm assuming it is a lurch forwards? Your lack of engine stability at low speed on a light throttle does seem to point to an engine control rather than gearbox issue. If you can replicate the lurch by briefly and lightly touching the throttle while stationary, then that would be more evidence pointing in the direction of a sensor controlling idle speed which is on its way out. Were your replacement MAF sensors new or recycled used ones? If they were new, then my next port of call would be the throttle position sensor. Another common problem is an injector sticking open occasionally. All should have recorded a fault code already. Of course, you know your own car better than anyone, but I would certainly investigate engine control before the gearbox.....
 

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Discussion Starter · #6 ·
First, thanks for the input, much appreciated :)

Regarding the lurch after coming to a stop, I'm not aware of hearing the engine RPM rise, just feel a sort of movement through the driveline. It's a bit like, if you're stationary with the car in neutral but holding the brake pedal, then you put the car in D you feel the transmission engage and start to try to pull against the brakes. All that, except the car was never moved out of D, if you get what I mean?

I agree regarding the variable engine rpm at low load/throttle when cold, that could simply be because the car is still in open loop for emissions/mixture, SAI still operating etc. as well as the possibilities you mention. The car has done about 94k miles and just past the ten year mark from the build date so due for new spark plugs too, according to the official service schedule.

The MAFs were new, although they were not purchased through Jaguar, they are still the official Denso items just missing the Jaguar part number.

How would one go about diagnosing the TPS, will fault codes be present if there's an issue?
 

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Theres a few TSBs on this, basically its an adaptive learning problem, to cure it both the TCM and ECM need to be reflashed. I've got the lurch as well, waiting until I change the gearbox fluid etc next year and will get the reflash done.
 

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My 07 XKR did it to some extent for the whole time I had it. My X350 did it as well and I assume that it is the gearbox switching to 1st gear. The XKR GT tune file for the TCM from Cambo seemed to help quite a bit. Resetting the TCM adaptation with SDD seemed to help for a little while as well.

I was relieved to find that my new '10 XKR doesn't do it!
 

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Mine did the lurch (thump in the back just after coming to a stop) around 60k miles. Gearbox oil change and resenting the software cured in although from time to time I can feel it but more of a delicate thump. It got so bad that I would always flip to manual or neutral just before a stop. If your oils been changed recently might be worth just ‘doing’ the software?
 

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Discussion Starter · #15 ·
So mine isn't really a thump as such, just a small bump - as in my post on the first page, it feels like if you have the car in N while holding the brake pedal and you change into D, you'll feel the engine engage with the transmission. I do often pop the car into N when I come to a stop if I know I'll be sat for any more than a few seconds (e.g. traffic lights) so I don't always feel it and it doesn't happen in N.

I'll run some diagnostics and maybe see if I can reflash the transmission with SDD, I did try resetting the transmission adaption learnings a couple of months back, maybe I should have done the ECU as well.
 

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Thanks Shmee, I have seen a few listed over on thelurch.com although I didn't see anything specific to my particular lurch. Does yours happen like mine, a few moments after coming to a stop?
After coming to a stop and engaging parking brake, it's annoying but not seriously so. Stops doing it after a good run, might be the oil is not fully warmed through and the mechatronic valves are slower to respond.
 

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8bit, have you ever had the gearbox oil changed? Although my XKR behaves perfectly, my new-to-me 130k mile Volvo XC90's gearbox seems a little unsettled sometimes and I've been reading forum threads to soak up knowledge about this. Lots of people say that a gearbox oil flush and change fixes these sorts of behaviours. When I rang a local specialist to book both the Volvo and the Jaaag in for an oil change his first question was "Does it ever lurch when coming to a stop or between gears 3 and 4?"

Oil choice on our 6HP26/6HP28 gearboxes is a bit of a minefield, but everybody seems to be recommending that a change is done every 60k-80k miles regardless of what car manufacturers claim about gearboxes being sealed for life.
 

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Discussion Starter · #19 ·
Yeah I had it changed in March 2015, so about 2.5 years ago. I'll have done maybe 7k miles since then.

I have read of people having the fluid changed and ending up with the transmission feeling worse. Someone else I spoke to spoke of a theory that the friction material in the clutchpacks inside the transmission itself end up wearing as the fluid ages but the material gets suspended in the fluid. When the fluid is changed the friction material is gone so the clutch packs don't work so well. The thinking there is get the transmission serviced much more regularly from new (like 20k miles) but if it hasn't been done by about 80k miles or so then don't change it because more harm could come of it than good.

I'm going to monitor this for a while before doing anything much I think. I don't do a lot of miles and I've half a plan to change the car next year anyway.
 
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