Does anyone have any idea what could cause a small rpm fluctuation? When driving at a steady speed, my rpm will fluctuate around 100rpm on and off and it keeps doing it as long as I'm holding steady pedal pressure. Doesn't seem to be any negative effects, but I'd like to get it taken care of. I checked for codes/faults and do not have any. 2013 LR4 with 78k miles. Thanks.

 

Have you used an injector cleaner lately? I mistakenly put regular gas into mine once then added some cleaner, did what you describe a couple days then went away.

 

had the exact same issue. its the torque converter locking up..

solution is to change the transmission fluid and filter. use the aftermarket filter/pan that comes separately in order to replace without removing any other components.

add fluid, drive for a day.
mine still fluctuated RPMs at this point.
drain and refill, again. problem solved.

the second drain/fill will get more of the old fluid out, and allow the torque converter to stop locking up.

 

@KMET - I have not used injector cleaner lately. May be something worth trying as I'm just over 75k miles now.
@Daytonars7 - I will give that a shot. I did replace the filter/pan and fluid a few months back with the kit you are describing. I have not done a second drain and fill though.

 

as much as i wish it was another issue for you, i had the exact issue you are describing. its called RPM hunting. 99% of the time its the torque convertor locking/unlocking due to fluid contamination.

my car had 140k miles when i noticed this. it was a huge relief that changing the fluid a couple times solved the problem. because the alternative of a new torque converter was a cost i did not want

fyi, i used valvoline maxlife ATF. saves a lot compared to OEM fluid. works great.
https://www.walmart.com/ip/Valvoline...IaAs9CEALw_wcB

 

@Rackolamb1 Please follow up with your results. I have the same rpm hunting issue and I will be looking into it soon as well. I did just do a full top end rebuild with fully rebuilt fuel injectors. It continues to do the rpm fluctuation, so I highly doubt that it is due to fuel injectors.

I agree with @Daytonars7 that it is likely a torque converter issue. My search brought me across a thread on another forum where there was someone who is very knowledgeable about the LR4 transmission. He showed some diagnostic graphs of the transmission lock up commands and he seemed to suggest that when this happens the torque converter needs a rebuild. There was at least 1 or 2 people on the thread that sent their torque converters out for rebuild which fixed the issue.

This is the 1st time that I am hearing that a simple fluid exchange could remove enough contamination to fix the problem. If so, I would love to hear your results.

 

Having the same issue. Seems to stop when I put in in manual mode.

 

I have the same issue on a 2010 with 260k km; not resolved yet.

From my research I gather there could be a few issues that lead to this surge, broadly categorized into engine issues and transmission issues:

Engine issues (throttle hunting) may cause computer to hunt for desired output
1. Dirty throttle body
2. Dirty injectors
3. Vacuum leaks
a) worn out PCV
b) failures in the intake plenum gasket
c) etc
4. Spark plugs
5. Accelerator pedal sender

Transmission issues
1. Dirty fluid
2. Worn out torque converter
3. Valve body gaskets/seals/risers

There seems to be some consensus on how to troubleshoot:
1. Check if it still hunts on cruise control. If it does not, suspect the accelerator pedal sensor
2. Check if it hunts in manual shift mode (command shift). If it does not, the issue is most likely transmission because command shift increases line pressures and hold the torque converter better
3. Check if it hunts in OD with brake lightly applied (unconfirmed, apparently pressing the brake makes TC unlock? I do not believe this to be necessarily true) if stops hunting, torque converter issue
4. Check if hunt under load at speeds below 35kph (25mph) this is where the converter is always 100% unlocked. if stops hunting, torque converter issue

Mine hunts in all gears and all transmission settings, regardless of cruise control, so i suspect engine management, and am proceeding as such. However ordered the fluid for the trans because it is time anyways.

My troubleshooting plan is as follows:
1. Clean TB & MAF (completed)
2. Clean injectors (completed, PEA-based cleaner)
3. Check/change PCV (completed)
4. Check for vacuum leaks (completed)
5. Check spark plugs (pending)
6. Change transmission fluid (waiting for parts)

On the topic of transmission i also ordered some deglazing agent (lubeguard) and will add that to first dran&fill, then take most of it out with second drain & fill.

Anyhow, these are my thoughts on the matter, hope some of it is helpful.
Cheers,
Tom

 

I have a resolution to mine, not sure what the OP found out.

This is what mine was. As a troubleshooting step I used a tube of Lubegard Instant Shudder Fixx. It contains an add pack that may be depleted from the fluid, as well as some compounds to deglaze the clutches.

Throttle hunting is gone.

My fluid arrives in a week, and i intend to do 2x drain & fill and add another tube of this stuff to the final fill.

 

Thanks for the follow-up. It's encouraging to hear more evidence that it may be as simple as a fluid change. I got some fresh fluid a few days ago and will try the exchange as well. Did you change the filter and pan to one of the new updated ones? Or did you keep the same pan/filter combo?