Land Rover Discovery 3 loss of power when towing caravan

Submitted: Thursday, Mar 03, 2022 at 18:20
ThreadID: 143326 Views:5253 Replies:7 FollowUps:3
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Towards the end of long inclines the Disco has a tendency from time to time, when towing a 21 foot caravan, to go into a form of a sluggish "limp home" mode. You can feel the power drop off, kick down transmission change not responsive. The good news is that it continues to pull the van holding reasonably steady revs and once over the top of the incline, returns to normal operation. The problem is exacerbated on hotter days. The vehicle is serviced in accordance with service intervals, initially with Land Rover dealer then by two Land Rover specialist service centres here in Melbourne, AMV and Rover Range. Nothing shows up on engine diagnostics to help the service guys understand the cause. LR initial solution was to change transmission oil to no avail, other efforts including remapping the engine have not resolved the problem.

I am hoping there may be some better advice amongst Explore Oz members

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Reply By: Rocket Rod - Thursday, Mar 03, 2022 at 18:57

Thursday, Mar 03, 2022 at 18:57
Suggest you become a member of Australian Land Rover Owners forum as there will be a host of information awaiting you there but possible causes are split inlet manifold or split turbo pipes. Remapping, although good for other reasons, won't solve something that is mechanically failed.
AnswerID: 639701

Reply By: Michael H9 - Thursday, Mar 03, 2022 at 19:58

Thursday, Mar 03, 2022 at 19:58
Maybe there'a a small split in the intercooler hose? I've had a similar experience with a Landy.
AnswerID: 639702

Reply By: Member - Captain (WA) - Thursday, Mar 03, 2022 at 20:31

Thursday, Mar 03, 2022 at 20:31
Had a similair issue many years ago in my LC200 on a very hot (>42C) day when towing. Seems to lose a lot of power if trying to overtake, but otherwise engine ok at normal speed.

Have since found out that when transmission temp is too high it goes into a type of limp mode. I now monitor transmission temp (scanguage) and have installed a torque convertor lock kit. Havent had the problem since.

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AnswerID: 639704

Reply By: Keir & Marg - Thursday, Mar 03, 2022 at 22:12

Thursday, Mar 03, 2022 at 22:12
Certainly sounds like a transmission temp issue. Fitting an additional oil cooler is an option, but with the Pajero, I've installed a lock-up kit, which has resulted in the transmission oil temps remaining low. Previously during long climbs with the caravan behind, the transmission would stay in 3rd gear at the top of the climb whilst the transmission oil temp slowly reduced to normal. The lock-up kit prevents that temperature rise as the oil doesn't get hot. The other benefit is an improvement in economy of about 2L/100km.
AnswerID: 639706

Follow Up By: OzzieCruiser - Thursday, Mar 03, 2022 at 22:20

Thursday, Mar 03, 2022 at 22:20
The topic is a Land Rover Discovery not a Pajero - the LR already has a lock up torque converter that locks from 1200rpm.
FollowupID: 918766

Follow Up By: Keir & Marg - Friday, Mar 04, 2022 at 10:14

Friday, Mar 04, 2022 at 10:14
The Pajero has OEM lock-up too, but only in 4th and 5th, and the lock-up often doesn't work in 5th when towing; this why most people get better economy in 4th when towing, rather than leaving it in drive.
I am not aware of how the TCU controls lock-up in the Land Rover gearbox, but it is common for OEM lock-up to only occur in the top couple of gears, whereas for towing uphill, and engine braking downhill, you really need lock-up in lower gears. The additional benefits are lower ATF temps and better economy.
My suggestion to consider a lock-up kit is independent of the type of vehicle, but I mentioned the Pajero as an example of the benefits of fitting such a kit.
Whilst I am aware that there are quite a few after-market lock-up kits for Toyotas, Nissans and Mitsubishis, I am not aware of one for the Discovery.
PS. I have owned three LR vehicles over the years - a RR, a Discovery, and finally a Freelander. Fantastic vehicles when they are running, but the last two were genuine off-road vehicles i.e usually off the road in a garage somewhere being fixed!!
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Follow Up By: Gronk - Friday, Mar 04, 2022 at 10:20

Friday, Mar 04, 2022 at 10:20
Has the LR got a lockup torque converter that stays locked ? I’d say not…just like most auto boxes.
No matter what make of car (4wd), the auto will change down going up hills, and if towing a big load, the auto will not be locked.
A lockup kit will stop a lot of slippage as the auto will be “locked” in any given gear.
So to answer the OP’s question…..yes the auto COULD be overheating and going into a limp type mode. The OP should run a Ultragauge or similar and keep an eye on his trans temp.
FollowupID: 918777

Reply By: Jarse - Friday, Mar 04, 2022 at 08:06

Friday, Mar 04, 2022 at 08:06
Yep, possibly an intercooler hose. There have also been instances of cracked inlet manifolds, leading to similar symptoms you describe.
I believe the transmission response is intentionally programmed as part of the limp mode.

Hope you get it sorted.
AnswerID: 639712

Reply By: patsproule - Sunday, Mar 06, 2022 at 20:27

Sunday, Mar 06, 2022 at 20:27
It will be de-rating (form of self protection) due to excessive inlet air temps (IAT) or excessive transmission temps from the long climb. The tell-tale is that it returns to normal quickly. A lot of vehicles do it, some more noticeable than others. If you have a scangauge or similar you can monitor them, and the boost pressure. I'll bet the de-rate kicks in around 100 degrees IAT.

AnswerID: 639742

Reply By: tim_c - Friday, Mar 11, 2022 at 11:54

Friday, Mar 11, 2022 at 11:54
It could be an exhaust temp. protection, assuming it's a diesel. Some diesels will detect high exhaust temps and limit power to prevent the exhaust temp. getting hot enough to roast (or melt) your engine.

If you fit a exhaust temp. gauge (probably not necessary if the vehicle is already limiting the temp.), you'd be able to see the temp. climbing, particularly towards the end of a long incline while towing in hot weather - the longer the climb, the harder it is to keep the temp. down. Once you're over the crest and going down the other side, the exhaust temp. will usually drop quite quickly.
AnswerID: 639801

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