2002 4.2 XKR surging under light throttle

[jamesc69]

Hi All

Weird one this.
Car seems to surge on light throttle only.
Feels like its being held back!
Only happens on light throttle. No prob when booting it!

No misfire, nor are any warning lights lit.
Revs dont appear to increase on the tach, but definately a sensation of surging forward then easing back on constant throttle opening.

If i had a clutch pedal, I would say it was like the clutch was being half applied and released constantly!

Car booked into XJ Services in Wigan.
They spent a couple of hours on it , but could not identify the cause.
No air leaks, fuel pump OK, timing OK, lambda sensor checked OK. Gearbox apparantly OK, no fault codes.
He thought it was almost as if the mixture was wrong, running rich or lean.

Any ideas guys as we appear to be running out of ideas?

thanks James

[ringram]

An obd scan tool would show you. Its probably timing or fueling as you say. A bit hard to figure out without knowing if its fuel, spark and/or airflow thats messing about. You could check stuff like your throttlebody to make sure its not gunked up, which would have most effect at low throttle, but thats just trial and error stuff until you log the engine operations at the time. If you can fault it all the time ask the dealer if they have a portable scantool and go for a drive with them.

[brdave]

I have a 2003 XKR and have had similar slight surge. It usually happens when the car is not fully warmed up and driving around 40-50 mph. I think that it is the transmission not being sure whether it wants to be in 5th or 6th gear. FWIW
good luck
brdave

[ringram]

A lot of ECM's trigger events based on Throttle position. Things like deceleration fuel cut off, which cuts fuel when you are decelerating, also transitions between base spark tables and running spark tables used for idle and near idle and normally optimal driving etc. If your throttle position sensor from the pedal is right near/on this point you may be switching into and out of a certain mode. Now you would have thought a stock XKR would not exibit this, but you might find that a calibration update was released to address this etc. You can ask the dealer if you have the latest ecm calibration. Otherwise as mentioned it could be a mechanical issue preventing proper control, maybe dodgy tps sensor, or gummy throttle etc. An engine scanner will show what parameter is varying and thereby indicate the likely cause

[jamesc69]

thanks for your input guys.
ringram, you suggested taking the car to a local dealer equipped with a portable scantool. Will this generate any error codes, bearing in mind no error codes are showing incar on the warning / error system?

James

[Beemer-5]

My transmission never knows what i want, either!
Can this be altered at all?

3rd gear cruising along, then foot part-way down and we get 4th instantly!

Only will it change down if i boot it!

[Triple7]

Beemer-5 said:

My transmission never knows what i want, either!
Can this be altered at all?

3rd gear cruising along, then foot part-way down and we get 4th instantly!

Only will it change down if i boot it!

I must admit, that was the biggest annoyance I had with my 4.2 6spd XKR. I hated the fact it was never in the gear I wanted. I so much preferred my previous 4.0ltr XK100. In the end I used the 'J' gate most of the time, but ultimately sold it. First model I ever bought without test driving it first, never again.

The 6 speed box on the new XKR is however puurrrfect.

G

Why not get the paddle shift option fitted by Racing Green?

Edited by Triple7 on Tuesday 20th November 18:04

[Beemer-5]

Could do i guess, would depend on cost.

[Triple7]

I seem to recall it's one of the cheapest mods to do.

NormD has it and loves it.

G

[Tame Technician]

Its a software update, your local dealer should no all about it.

When I worked at a Jag dealer, 1998 - 2005, I did loads of them. That and a thump as you come to a stop were the only real complaints with the 6spd ZF box. Both can be minimised if not eradicated completely with a flash update.

[ringram]

jamesc69 said:

thanks for your input guys.
ringram, you suggested taking the car to a local dealer equipped with a portable scantool. Will this generate any error codes, bearing in mind no error codes are showing incar on the warning / error system?

James

No error codes, but if they log spark and airflow etc you should see what is varying and causing the issue. However as mentioned make sure you are on the latest ECM code to eliminate a dodgy calibration as being the cause.

[Beemer-5]

Beemer-5 said:

What should i expect to pay for the update/s?

???

[Tame Technician]

The surge is cause by the torque converter, or more acuratly, the way the Transmission Control Module operates the lock up function, of the torque converter. Measuring engine management data with data logger wont find anything.

All the updates I did were under warranty, so were free. Out of warranty the cost would be around 0.5 hours labour, at what ever you local dealers rate is. I managed to get the technical bulletin number for the surging fault. Its TSB S307-14. Tell the jag dealer you need this doing and they should be able to give you a fixed price. Its stated on the bulletin, sadly i dont have a copy anymore. Who ever answers the phone, may have to speak to a technician and then call you back, only the most switched on service advisor's will know what the TSB is. They may add 0.3 hours to check the fault memory first.

Remember what i said about minimising the symptom, it may not go away completely. But 90% of customers were happy with the cars I did, so should be fine.

[jamesc69]

thanks tame technician, very helpful indeed. Fingers crossed this is the problem. Car booked into Rybrook Jaguar Warrington Wednesday, will let you know.

[jamesc69]

Ok, car back from Rybrooks. Surging does not appear to be transmission control module issue.

Rybrook diagonistic shows problem with Oxygen sensor (more specifically bank 1, sensor 2).

Quoted £560 fitted! (£250 for 1 x sensor! and 2 x hours labour). Apparantly the 4.2 has 2 x Oxygen sensors, upflow and downflow

I have managed to order both sensors for £147 from www.britishparts.co.uk. I have been assured that are the correct ones.

Just need to find a competant local garage as i believe that these sensors are a bugger to get access.

James

[jamesc69]

Hi Melhook

Can i pick your brains? Don't know if you have seen my previous post below re car surging / hesitate.
2002 4.2 XKR 6 speed.

jamesc69 said:

Hi All

Weird one this.
Car seems to surge on light throttle only.
Feels like its being held back!
Only happens on light throttle in top gear only, only when car has warmed up. No prob when booting it!

No misfire, nor are any warning lights lit.
Revs dont appear to increase on the tach, but definately a sensation of surging forward then easing back on constant throttle opening.

If i had a clutch pedal, I would say it was like the clutch was being half applied and released constantly!

Car booked into XJ Services in Wigan.
They spent a couple of hours on it , but could not identify the cause.
No air leaks, fuel pump OK, timing OK, lambda sensor checked OK. Gearbox apparantly OK, no fault codes.
He thought it was almost as if the mixture was wrong, running rich or lean.

Any ideas guys as we appear to be running out of ideas?

thanks James

I have since taken the car to main dealer whose diagnostic showed failed Oxygen sensors. I have replaced both and the problem persists.

Dealer has also assured me that the gearbox does not need flash update.

Any thoughts, car has done 105K, might the spark plugs need replacing?

Thanks
James