Ditto on what fmertz says above. Here's the method I found online for a X100 accelerator pedal reset (especially after doing a "hard reset" and after adjusting the accelerator pedal cable):

With ignition switch in Position II, (on, but not started), slowly press accel pedal through the kickdown detent all the way to the floor; hold 5 seconds. Release pedal and repeat one more time.

Then: Start engine, idle until normal operating temp is reached. Switch off.

Then: Restart, idle for 2 minutes.

Then: Apply foot brake, shift to drive, idle for 2 min.

Then, drive for 5 miles of varied conditions.

 

Hi guys
Thanks for the info on throttle readjustment, I'm going to try it in the morning. Also getting her cats and 02 sensors checked tomorrow by exhaust garage, so hopefully between trying the throttle adjustment and the cat check them we will begin to narrow down the list of suspects.

I did check the throttle valve physically opening and closing with the pedal electrically and it was showing 95% on the obd2 when fully depressed so needs adjustment anyway to get 100.

Will update hopefully with good news tomorrow.

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Update...
Problem persists
I have had the cats checked, they are free flowing, but the garage who checked the cats suspects it is actually gearbox related and the ecm is reacting to the gearbox slipping.

So I took it to a m8 of mine who is also a mechanic and he says the same thing it appears to be slipping and the engine is responding to this gearbox slipping.

So next plan is to check all ABS sensors to confirm info they supplying gearbox (sensors appear OK on code reader), then next will be check gearbox fluid level and then worst case torque converter or tcm( gearbox oil change was done about 2k miles ago).

But seems to be the gearbox... And what I initially saw as the rise then drop in engine rpm seems to be the engine responding to the slipping.

I will update hopefully next week.
All suggestions welcome.

It is a huge tease, to have the powerful v8 engine, ticking away but not pulling, how I miss prodding the throttle haha.

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It seems unlikely that the computer would detect the gearbox is slipping yet not set a code for it - it certainly does on the 5 speed ZF boxes.

 

Do you have P1111 instead of P1000 yet?

If not, which monitor(s) is/are unset?

(They'd be hints as to what's wrong.)

Also, did you figure out the fuel pressure problem? If it's dropping as it appears then of course power can't be produced.

 

I also found this a bit strange, but they both individually came to the same conclusion and so hoping we can at least rule it out as I'm at a loss as to what's causing it.

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Sadly not still a p1000, is there a way to force it to p1111.

The fuel filter has now been changed so fuel seems to be stabalised and responding normally, the filter was dirty but not blocked, deff original tho.

My icarsoft shows no faults other than p1000 and driver seat position sensor and my mates delphi reader the same.

 

When you say which monitors are unset do you mean, what's holding the p1000 code, and if so is there a way to see that? Sorry just wanna make sure I fully understand so I can check it for you.

 

Read up on "OBD monitors" and then see which of yours has/have not set. Then try the associated drive cycle(s) to set it/them.

Premature worrying about gearbox slipping, an incredibly unlikely thing with no gearbox code seems to me.

 

Update.
A huge improvement but not quite there yet.

It turned out the front left wheel bearing had alot of play, and so wheel sensor was unable to pickup the readings correctly.

This definately helped, as the car pulls better now and suddenly can feel a softer ride suspect the cats suspension maybe now correctly working as i think I read somewhere that the wheel speed sensors are used for it too.

Mechanic couldn't believe the car made no sounds indicating the wheel bearing.

So to finalise this issue, it seems that the transmission is now holding gears too long, sometimes just hanging at the top end.

Could this be the tcm needing to relearn after compensating? If not an option, has anyone any possibilities of what to try?

I will also be able to check the obd monitors tomorrow as previously advised.

Many thanks
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The transmission will re-learn your driving preferences after a hard reset; it just might be doing it after resolving the wheel bearing issue. There is a complex adaptation drive sequence that will expedite it (helps to have an assistant to call out gears and rpms), but normal driving for a few days will do it just fine. If you're not throwing any error codes, it's not a bad idea to adopt a wait-and-see attitude. How many miles have you put on your car since changing the wheel bearing? Keep some notes to see if you actually realize a change in shifting patterns over a few days. Note: I had a great XK8 friend here in Las Vegas that graciously re-flashed my ECU when I had a hard, 1st-to-2nd transmission up-shift issue, and he said that he erased over 15,000 stored adaptations from the ECU's memory. We then did an adaptation drive together, and my car's shifting has been butter-smooth for almost 5 years and 24,000 miles of driving now.

Concerning your throttling issue, have you inspected the top of the throttle body yourself? I know you said the previous owner recently replaced it, but I would want to personally check and make sure it's clean, and possibly spray some throttle body cleaner through the intake while the car is running (good to have an assistant there too, to help keep the engine running but not exceeding 2,000 rpm). I saw significant improvement in the engine response of my '05 barn-find from one application of Berryman B-12 Chemtool, but there are many good throttle body cleaner products out there.

 

The transmission will not upshift if it thinks your foot is on the brakes. It "knows" through the brake switch, so either the brake switch is defective (pretty common), or the adjustment on the trigger (there is a ratchet) is off and always reading as if your foot is on the brakes. This adjustment is subtle, and can trigger based on temperature, on a sometimes basis. Of course your brake lights will be on under these conditions. Maybe have someone follow you to check this, or use your code reader to read the condition of the switch as seen by the ECM.

FWIW, I am still unconvinced there are no codes for this. The code reader I have has "modes" of operation, one OBDII mode as well as a mode (icon) per "brand" downloaded in the reader. Make sure you use the JLR mode for the specifics, not the generic OBDII.

 

That's very interesting, I certainly will have someone check by driving behind me tomorrow, not something I wud have considered at all so will Check it out.

I have a supposedly JLR specific Icarsoft but it is throwing no codes, dash is clean too, and mechanic friend used his delphi, and the same all we can see is the passenger seat position error.

I have just noticed however that after start I get a flash od dsc fault then it immediately clears, just a flash then gone.

Its so hard to tell if its the transmission or the engine, causing the loss of power at high rpm. The car sometimes feels like it is slipping and sometimes judders and holds the revs, but if I back off the throttle it slowly gains speeds and shifts properly. Then sometimes it holds the gears.

Mechanic was saying his own next port of call wud be putting it on the dealer software to get the tcm scanned.

If I plant my foot to the floor the car tries to accelerate but bogs down and judders, but sometimes this is replaced with a sprightly acceleration then not letting go of revs.

​​​If I keep foot lightly on accelerator all is normal, very frustrating.

Recap for thread so far:

• Doesn't seem to vary with warmup eg engine temp.
• Gears on left all seem to individually shift and I can feel the 6th in drive and in drive under light acceleration or normal driving
• Seems to shudder if I try to accelerate at a medium to hard acceleration or gears do not downshift.
• No differeence with sport mode on or not
• No difference if left or rhs of jgate
• Previously had left front wheel bearing worn with play resulting in non annuciated abs fault but code reader did show this.
• Driven 60 miles approx 10 cycles since the wheel bearing resolved but still an issue with acceleration.

I

 

Il get another look at the throttle body and make sure all looks good, I did visually check the butterfly was moving as expected and checked position on reader correlated.

Thinking of doing a video of the obd readings while the issue is happening (safely of course) to see if it triggers or confirms any suggestions or suspicions anybody may have seen.

 

So the only one not completing is one called rather vaguely components monitor.

The others all seem complete.

 

So tonight I got a DSC and ABS fault appear on the dash while driving, im very happy to see codes, just hope they are related to the problem im experiencing and not a new issue. When I put it on the JLR ICARSOFT it said no faults in the ABS bt i now have :

1. U2012- Communication Bus error- non SCP
2. B1595-Ignition Switch Illegal Input Code
3. U1041- SCP Vehicle speed signal - invalid or missing message
4.B2368- Column Adjust switch, out f range

I restarted the car , and drove for a bit to try see live data, and as i left the driveway, the warnings vanished.

Any ideas if this might be related to the transmission hiccup at higher revs, the speed signal is concerning to me.

This happened at night, and im wandering if its a symptom of a knackered battery just as in the past with my other jags i almost use the dcs and ABS as "Replace battery" warnings. Im not sure if a knackered battery could cause the transmission problems tho, but certainly interested to hear the feedback and thoughts.

I will test the battery tomorrow and check all is good, if not then il replace.

 

Very perplexing; let's hope it is something as simple as a battery that needs replacing. My first indicator of a tired battery was the windows failing to go back up after closing the door(s), even after resetting them.

 

Ok so had a friend follow me and he said, brake lights only came on when i was actually braking, no signs of it intermittently coming on.
Any ideas where to go from here?

 

Have you checked the condition of the motor mounts? They are liquid filled. Some report seeing a purple fluid as evidence of leaks. With the hood open, maintain pressure on the brakes to remain stationary, put the car in Drive and press on the gas. Broken mounts will allow for the engine to rock in relation to the rest of the body. This rocking can cause large air gaps to temporarily open and bog down the engine.

 

OK so transmission fluid swapped and filter replaced to make sure, still slipping, so seems the gearbox has had its day. The good news is I have a zf6speed lying there from my old stype which I got rid of last year, so mechanic gonna try swapping them around.

Hopefully this sorts it out.
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