Fluctuating RPM's at constant throttle (throttle hunting, surging, gear hunting)

[Houm_WA]

Hmmm. Something like that could drive me mad...

 

[bbyer]

This winter, I have the same problem - engine surging, but if I shift into a manually selected gear and drive for a few minutes, the problem disappears for the day. I have 275,000 km (170,000 miles) on the 3 and have changed the tranny oil three times now since new.

As the first post of this thread said, it is not when the engine starts cold but maybe five minutes into the morning drive and the heater is making some heat. The surging only lasts for two or three minutes if I ignore it.

I assumed the surging to be the torque converter hunting or that Mechatronic valve block since locking it into a gear hides the problem.

Right now, it is not a big deal and I also assumed it is a cold weather thing so have done nothing - will wait and see what the spring months bring. I would really prefer a bad thermostat being the solution rather than bits, (well big expensive chunks), within the tranny.

I have a Scan Gauge and it does not show any temperature fluctuation on the way up, (but it may be well damped); instead I just see a steady temperature increase to a max of about 195F, or if real cold, 185F.


This is a link to a 47 page LR pdf related to our 6HP26X tranny. The pdf has a number of colour cut thrus and a discussion of the Mechatronic valve block.

http://www.disco3.co.uk/gallery/displayimage.php?album=5059&pos=11

 

[Globetrotter]

Have you tried the old faithful "Dr Tranny" this may fix your problem

 

[bbyer]

Hide, rather than fix, is what might at best happen with any of these transmission "treatments".

Dirtying up the tranny oil is another fix - perhaps with iron filings - not a long term fix but long enough to exercise the options.

This is why a problem automatic may not function all all, (well reverse gear probably still works, hence one can back it off the hoist), after an oil change. New clean oil does not contain the contaminants that was allowing the worn tranny to sort of function.

 

[zulu]

Hi all..its been awhile since i posted. Guess thats a good thing? But i have been creeping and reading everyone's experiences. Thanks for sharing. My 2005 hse is also doing the same thing as described by the original poster. But i will add to it with a slight hum coming the power train after the fluctation slow downs and settles around 2000 rpms and at low speed. While in sports mode.. No fluctations..but humming will still happen around 2000rpm. My rig is now at 164,000km.. Love my lr! Any feedback will be appreciated. Thanks

 

[bbyer]

Hi all..its been awhile since i posted. Guess thats a good thing? But i have been creeping and reading everyone's experiences. Thanks for sharing. My 2005 hse is also doing the same thing as described by the original poster. But i will add to it with a slight hum coming the power train after the fluctation slow downs and settles around 2000 rpms and at low speed. While in sports mode.. No fluctations..but humming will still happen around 2000rpm. My rig is now at 164,000km.. Love my lr! Any feedback will be appreciated. Thanks

Per my post #12, I was having somewhat similar concerns re my 2005 LR3 re the tranny and shifting, but in cold weather only.

Rather than a tranny problem, I decided it was probably a temperature sensor problem - cheaper to think that - so in Feb of 2018 I changed out the engine oil temperature sensor, LR p/n LR 065234. This seems to have resolved the hunting problem. I now have 357,000 km on my 4.4L V8 HSE.

As always, LR has a complicated way to determining temperature. There is both that oil temperature sensor and also the water temperature sensor and they both feed to the engine computer. From there, some math combo of the two signals go to the temperature gauge on the dash, the tranny, and who knows where else.

One can best change the oil sensor during an oil change as it is located near the oil filter.

The water temperature sensor come free when you change out the plastic thermostat housing, Lr p/n LR 005631, something I do every few years. You get a new thermostat properly installed, a new temperature sensor and new plastic for not much more than the price of the thermostat and the labor is easier.


https://lrbritishparts.com/?product...6-09-range-rover-sport-05-09-lr3-new-lr065234

 

[zulu]

Thanks bbyer.. I'll go do the simple fix of the oil temp sensor first and see where that leads me.

Meanwhile.. Driving in the sports mode is kind of fun. But still not sure why the engine will humm around 2000 rpm while at low speeds.

 

[armozo]

I’m not sure the LR3 has a viscous clutch fan that is electronically controlled, but my LR4 would do that when the clutch was stuck.

Worth checking out.

Thanks bbyer.. I'll go do the simple fix of the oil temp sensor first and see where that leads me.

Meanwhile.. Driving in the sports mode is kind of fun. But still not sure why the engine will humm around 2000 rpm while at low speeds.

 

[zulu]

I’m sure the LR3 has a viscous clutch fan that is electronically controlled, but my LR4 would do that when the clutch was stuck.

Worth checking out.

Thanks vlonjati.. Is that the only indicator of a stuck clutch fan? Any other indicators?

 

[armozo]

In a cold morning listen for sharp sounding metallic clicking. I don’t thing you’d miss it, it is loud.