I have recently noticed that when driving my 1997 XK8 at low revs (1000 -1500 rpm) there is a slight “surging” of the engine note. A small oscillation of the rev counter can also be seen between these values. This normally happens whilst driving through an urban area at speeds of up to 40 kph. Once above 1500rpm the surging disappears. No DTCs are recorded. Any thoughts? Many thanks.

 

In 2011 I had a similar issue in my 2005 XJ that turned out to be the torque converter not locking up properly. Consistent but subtle RPM fluctuation was most noticeable at steady speeds like on the highway. After replacing that all was back to normal. I was fortunate that the car was still under Jaguar extended warranty.

 

Dear Rothwell,
I must admit that I have never noticed the revs to vary at higher speeds & low revs only at low speeds & low revs.
I´ll be sure to check this on my next outing!
Cheers.

 

A vacuum leak can give you a slight surge.

 

Could also be related to issues with the TPS.

 

Yeah, a tps with a "flat spot" could indeed cause a surge as the thing overshot one way, then the other.
Don't know about XK8 or XKR but a lot of cars you can just unplug it. If surging doesn't go away, look 4 other causes.
Simply hooking up a vacuum gauge might reveal your problem, 30 seconds!

 

Could be resolved by reprogramming and reconfiguring the shift programme. Worked for me a few years ago. The TCM gets an update (trans reflash) and the adaptations get reset.

 

Hi Porterve,

I'm sorry to join your thread so late. I am attaching a TSB that contains diagnostic flowcharts that may be helpful.

If your engine idles smoothly without surging when in Park, one possibility that comes to mind is that your transmission may be "hunting" between two gears when you are traveling at steady speeds. Your transmission could also be slipping slightly due to low fluid.

Please keep us informed.

Cheers,

Don

 

Don thanks for posting this TSB !

 

Same very mild surging issue with my 2003. At 30 mph and 1300 to 1500 rpm the tranny is in 4th trying to shift into 5th causing the surge. When I move the J gate to 4th the surging stops. Definitely the tranny in my simple mind.

 

Hello all. Please accept my apologies for not responding sooner but have still got the front wheels off investigating a leak! As soon as I get a chance I’ll take her for a spin & let you know what I find.
Many thanks for your suggestions.

 

I have the same symptom in my 2004 XK8. Will be looking into a few of these suggestions here and will report back on my findings.

 

Well, happy to report that I seem to have solved my issue. I figured that I would start with some quick/easy stuff, so I started with checking tire pressure. Sounds strange, but I have heard that the rear wheels are a major input into the transmission logic on these cars. Pressure was good, so no luck there. I continued under the bonnet, starting with the MAF sensor. Undoing the air box, I noticed that the previous owner had installed a K&N air filter. I know many probably run these with good results, but I have concerns with the oil in the filter potentially gumming up the MAF sensor/ TB, so out she came. Ran up to NAPA and bought a replacement paper filter and some MAF cleaner. Gave the MAF a good blast, let it dry and reinstalled. When I pulled the air box apart, I noticed that the hose clamp attaching the intake tube to the throttle body more or less came off without me even having to loosen the clamp, so I could very well have had a nice leak from the intake tube directly into the TB. While I was this far, I also used a few blasts of TB cleaner on the TB for good measure. I put the air box back on with new filter installed, made sure the hose clamp on the intake tube was nice and tightly secured onto the throttle body this time, and fired her up and went for a quick drive. No “hunting” for the right RPM. She drove nice and smooth, holding steady RPM once at cruise. In summary, I’m not quite sure which of the above-mentioned issues was the true culprit, but it very well could have been a combination. Nevertheless, I am a happy camper and this made for a good 4th of July! Hope everyone on this side of the pond is enjoying their holiday, and to everyone else, a good weekend.