auto box does not change up under hard acceleration

Hi,
A question from rural France. I own a 2002 Disco TD5 Auto with 130k kms on the clock. Under normal driving conditions it behaves beautifully but under hard acceleration it refuses to change up a gear resulting in the engine juddering at ~3500 revs. I took it into my local dealer and he is equally perplexed. Any thoughts on the problem would be appreciated. I am a total dumbrain at mechanics so please keep it simple.

Sounds more like possible engine overboosting or misfire to me rather than a gearbox issue, the box should not cause the engine to judder, it should easliy rev with it all the way up to max RPM in any gear, this also seems true as it behaves under normal driving, and if the box had an "issue" it would probably be evident all the time.

Things to check :-

1. Engine ECU plugs not full of oil http://www.discovery2.co.uk/Injector_harness.html

2. Remove the intercooler hoses to check for delam, in particular the one on the bottom of the turbo(about 3 inches long)

3. Ideally the vehicle needs to be road tested with diagnostics plugged in to check the wastegate modulator is working and allowing full boost, if not and you want to replace as a matter of course (as they do fail) and dont want to pay for a dealer diagnostic session , http://www.discovery2.co.uk/wastegate.html

4. Check to see the wastegate arm from the turbo is "free" and not siezed, lubricate it with something like 3 in1 oil as you move it, a large screwdriver or prybar helps move it. It's on the top of the turbo and has a threaded rod attatched to it, it should move re-wards as you push it.

Wow...thank you so much for the advice. I will talk to my local garage and have them check the items you have listed. I am really impressed with just how knowledgable some people are and how they are prepared to put in some time to help others. Thanks again.

trevorg said:

Wow...thank you so much for the advice. I will talk to my local garage and have them check the items you have listed. I am really impressed with just how knowledgable some people are and how they are prepared to put in some time to help others. Thanks again.

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Hi there can I just clarify something with you, you say that under hard acceleration (pedal to the floor) the gearbox doesn't change up?

Bearing in mind that under hard acceleration the gearbox kicks down ie goes from 4th gear down to 3rd and even down to 2nd (depending on road speed) automatically, what is it that the gearbox is doing that you believe it shouldn't be doing?

After a bout of hard acceleration and you ease back on the pedal, can you feel the gearbox changing up back up the box ie 2nd to 3rd or 3rd to 4th?

If these symptoms are occurring at about 55mph with 'D' selected, are you sure it's not just the torque converter lockup coming in and out?

Can you give more info about this problem ie circumstances; road speed; gear selected etc etc?

I have no idea what is happening. You put the drive into D and accelerate away but if you floor the pedal the engine revs increase and when it gets to around 3500 the car kangaroos/jerks but the gearbox does not change up a notch....it is as if the engine has reached its maximum rev capability but the box does not change gear upwards to decrease the revs. If you accelerate away at a modest speed then everything works fine.

I need to add that this only became apparent when I took the car back to the LR dealer to fix a squeal on the rear brakes that he had rebuilt about 6 weeks ago (but that is another story). I went out with the mechanic to test the brakes, he drove the car (he probably learnt how to drive from Michael Schumaker) and that is how the problem manifested itself, he clearly drives with his foot hard to the floor all the time, as I drive more sedately (the gendarme are a tricky lot) I would probably never have known of the problem and indeed when I drove back home aftewards the car was perfect.

I will take it out tomorrow and report back on at what speed this happens and also how the box behaves when you back off the pedal.

Thanks for your reply by the way.

trevorg said:

I need to add that this only became apparent when I took the car back to the LR dealer to fix a squeal on the rear brakes that he had rebuilt about 6 weeks ago (but that is another story). I went out with the mechanic to test the brakes, he drove the car (he probably learnt how to drive from Michael Schumaker) and that is how the problem manifested itself, he clearly drives with his foot hard to the floor all the time, as I drive more sedately (the gendarme are a tricky lot) I would probably never have known of the problem and indeed when I drove back home aftewards the car was perfect.

I will take it out tomorrow and report back on at what speed this happens and also how the box behaves when you back off the pedal.

Thanks for your reply by the way.

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Just for your info, with my TD5 auto in D lock-up at 70mph (110kph) my car is turning over at 2200 rpm.

Also, as a method of identifying the engine performance but within reasonable road speeds try selecting '2' and then flooring the throttle and carefully analyse what happens throughout the rev range. Given enough space on the road you could easily be able to rev past 4000rpm.

Hello,
Thank you for the advice. I have done as you suggested and the result was:
1). In second gear only and foot hard to the floor the engine revved up to 4000 when I lifted off and changed up. At ~3000rpm the engine started to kangaroo/jerk (seems to power on and power off) and continued to do so up to when I lifted off the pedal.
2).Driving along in D I put the pedal to the floor and the gear box kicked down a gear and accelerated, again at ~3000revs the engine started to kangaroo/jerk BUT at ~3800 revs the box changed up a gear and the car continued to accelerate but in a jerky manner.
I hope I have not mis-lead everyone with my initial question but this type of acceleration is not my driving style and I genuinely thought that the box did not/would not change up....perhaps I should not have backed off so early!
So, if you can help me with the kangaroo/jerky manner of the engine I would be really gratefull.

trevorg said:

Hello,
Thank you for the advice. I have done as you suggested and the result was:
1). In second gear only and foot hard to the floor the engine revved up to 4000 when I lifted off and changed up. At ~3000rpm the engine started to kangaroo/jerk (seems to power on and power off) and continued to do so up to when I lifted off the pedal.
2).Driving along in D I put the pedal to the floor and the gear box kicked down a gear and accelerated, again at ~3000revs the engine started to kangaroo/jerk BUT at ~3800 revs the box changed up a gear and the car continued to accelerate but in a jerky manner.
I hope I have not mis-lead everyone with my initial question but this type of acceleration is not my driving style and I genuinely thought that the box did not/would not change up....perhaps I should not have backed off so early!
So, if you can help me with the kangaroo/jerky manner of the engine I would be really gratefull.

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Right, all that on the face of it sounds like normal gearbox behaviour, so it sounds like an engine fault.

Have a look at Urban Panzer's post again and his site which has excellent "How to................." explanations on it.

It could be a number of things but I always like to start with the cheapest which would be:

1. Clean the red ECU plug if it has any oil on it - use a spray brake and clutch cleaner to wash out the oil;

2. Buy a new wastegate modulator. See UP's site for the part number and how to do the job - should only take you about 30mins approx and is VERY easy to do plus at least it'll get that out of the way. The cost is about £20.

Then report back, please

Good luck

Dave

Will do...and thanks for all your help and advice. Will keep you posted on the result.
Best regards,
Trevor

I believe that a faulty MAF sensor can also cause this problem.

I occasionally experience this problem on my TD5, but never when I go out with the diagnostic tool connected

Hello everyone,
an update on the problem. My local LR dealer has put the disco onto the diagnostic machine and, as correctly identified, there was a problem with the injector(s) caused by oil in the harness.The wastegate modulator was OK. It also identified a further issue being that the engine was sending "the wrong message to the autobox" but they did not know what was causing this. They are currently waiting for a response from LR France on this "wrong message". So one problem solved and anorther identified. Thanks to Sastek on the reply also....perhaps this is the answer to the new problem....I will send a message to my local dealer and see what they say also.
I will keep you informed.
Bon journee.

Finally sorted. New harness fitted to the injectors and a new valve to the turbo (this is the best translation I can do from the garage bill) which was apparently causing some issue with the autobox changing gear. Now goes like s**t off a shovel.

Thanks for the advice and replies.

trevorg said:

Finally sorted. New harness fitted to the injectors and a new valve to the turbo (this is the best translation I can do from the garage bill) which was apparently causing some issue with the autobox changing gear. Now goes like s**t off a shovel.

Thanks for the advice and replies.

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I wonder if the part changed was the wastegate solenoid PMK100130 - £20?


Anyway, the most important thing is that she is fully operational again.

Dave

I think it probably was..the costs charged are about the same and the total labour time for fitting the harness and the "valve" including the diagnostic check was only 2.5 hours so not too bad. I showed the exchanges of mails from this site to the garage (the recovery mechanic speaks a litle english as he mainly deals with english people who have broken doen on the A26/A4) and they seemed genuinely impressed with the knowledge and the responses from you all with the result that they have offered to do a full diagnostic check on the Disco in january for free and show me how it all works. So if you see questions written in poor english from a french location it could be my local LR dealer tapping into everyones knowledge base.
Merry Christmas to all.

trevorg said:

You put the drive into D and accelerate away but if you floor the pedal the engine revs increase and when it gets to around 3500 the car kangaroos/jerks but the gearbox does not change up a notch....it is as if the engine has reached its maximum rev capability but the box does not change gear upwards to decrease the revs. If you accelerate away at a modest speed then everything works fine.

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In kickdown mode the box will change down and hold that gear until you ease off - at least in some cars. Can't remember if the Disco box does that. I'd have thought you should be able to rev a bit above 3500 though.

With the change in injector harness etc in kickdown mode it now revs up to ~4200/4500 with no signs of distress before it changes up a gear. I can now overtake with confidence!!!

Sorry for previous reply - I missed the second page of the thread. Can't seem to edit it out for some reason.