We noticed an issue with our 2003 XKR where at around 40-50 km/hr with light pressure on the gas the rpms seem to "stutter" (best way I can think of describing it). You can see the rpms flutter around 1500 like a subtle 1400 1500 1400 1500.... I checked on the ZF troubleshooting guide in the stickies section and looks like I found a similar description that read "Surge on fixed light throttle". My question - having zero mechanical ability, hubby has some - is the suggested fix only something a full on mechanic can do? Looks like it to me but thought I would check. Fix reads "Install coded access reflash using wds disc 42 onwards etc....
Thanks....

 

Kim,

A little car history and details would be helpful in diagnosing your problem ie mileage, service history etc. Does this "stutter" problem occur "all the time" or is it only occasionally, ie it happens only when initially starting the car. Does it disappear when engine is up to temp? Does it happen on the freeway or in urban traffic?

I ask this as it could be a number of things, like a loose throttle cable or dirty throttle body, which are hubby do-able DIY fix/cleans, or it could be the gearbox like you suspect. Before you go down the route of a specialist garage re-flash (which simply means software install in the Transmission Control Module), I would try to eliminate other causes.

When was the ATF (Auto Transmission Fluid) last changed? Don't believe the "Sealed for Life" claims. Again this is hubby home DIY-able, albeit in a more difficult "league" with plenty of info on this Forum on How-To including a famous Rev Sam YouTube video on the subject.

PS Didn't you have the 2003 XKR with a custom sun-roof?

 

Could easily be misfires, caused by such as bad coil(s) / air leak(s).

 

Thanks for the reply David.
Mileage is ~167000 km.
Transmission fluid change 6 months ago. Was doing it before this and still is after.
It doesn't seem to happen at higher speeds, only in that 40-50 km so urban traffic.
Seems to be after the engine warms up a bit but I'm not 100% sure we haven't had this shortly after starting driving (within 5 kms).
We did tighten up the throttle cable a bit and that did not change anything.

Sunroof is actually factory installed - didn't think I cared for a sunroof but use it all the time.
Now if I can just get the brand new stock brakes to stop squealing - we're all good. I'll let the dealer figure that one out.;-)

 

The transmission control is very sensitive to its input(s). The major one is the rear left wheel speed sensor (ABS sensor). The tire pressure and bearing conditions are critical. Also, sometimes, the reluctor ring gets loose and does not spin solidly with the axle anymore, causing false readings. FWIW, folks that have had the transmission fluid replaced with the (cheaper) Mercon SP have reported good outcomes on this problem (as compared to the ZF fluid). Keep in mind that the fluid ideally has to be flushed a couple of times in a row as the torque converter typically does not get emptied out, and some of the old fluid is left behind.

The ideal sequence is

• do a "major" maintenance (pan/filter, connector sleeve, bridge seal, tube seals, fluid)
• Have a dealer check the software level and do a reflash to the latest TCM code if necessary (one time thing)
• a couple of weeks later, do another flush/refill to get most of the fluid good as new. The Mercon SP shines here as it is so much cheaper.
• Follow that with a reset of the adaptations (a software/diagnostic port procedure) so the solenoid valves can be re-calibrated to the new fluid for maximum smoothness (this is adaptation takes place over the next 100 miles).

The other avenue is to double check the running condition of the engine. Start with checking the long term fuel trims, and work towards getting them down to less that, say, 5%. Sometimes throwing in a new air flow meter works great.

Best of luck, keep us posted.

 

As an update on this, hubby put some 5 in 1 fuel system cleaner in there that seems to have worked for the moment. The major maintenance on the trans was done with the fluid change ~6 months ago. Interesting on doing a 2nd flush/reflll, will pass that info on, Have spoken to our mechanic about potentially doing a software refash which he has experience with. Wil see how she runs over the next week and if the issue re-occurs will let everyone know... Thanks for the advice.

 

If the fuel system cleaner is helping, then you need to check the fuel trims next. These are numbers that can be obtained through the diagnostics connector. They are part of the OBDII standard, so there is no need for an expensive Jaguar code reader. Look for a cheap ELM327 device on eBay or Amazon. Then use your mobile phone to read the data with an app like TorquePro. This device reads (standard) codes as well as (standard) live data. Best is to read the long term fuel trims (both sides) at idle and then at 2500 rpm. These simple data points can help diagnose basic problems like air leaks on an aging car, or a bad air flow meter. Even if a code trips at +-25, as a driver, you can notice something above 5 with a slight lack of throttle response, lack of torque going uphill, etc.

Best of luck, keep us posted.

PS: Fuel Trims are basically how much fuel has to actually be injected vs. how much was calculated by the ECU, in order to maintain proper air/fuel ratio, for a given load and rpm. The number is a percentage above or below the calculated value. For example, a fuel trim of 10 means 10% more fuel than calculated was necessary.

 

Bought an ELM327 about a month after the car. Too bad it wasn't soon enough for me to use when it went into limp mode on a run. ;-) Has actually gotten more use on my 2016 Colorado but that's a story for another forum. Thanks again, will see what comes out of that.