Over revving

Chris mason 18 · Mar 7, 2016

hello I am new to this so please forgive me if I posting wrong

I have disco 2 td5 2000 auto

When I reach around the 30 mark when it goes to change gear it's as if it gets stuck and over revs can get over 4000 rpm before it will change gear then all of a sudden it will come alive and throw me back into my seat, this also can happen at 50 but not always.

I have checked the maf sensor looks to be OK have cleaned it with maf cleaner the air filter box is missing a clip and looks to be loose but from reading other threads this is not an issue took it to my local garage he has changed a few fuses and sensors ( not sure what ones have got a receipt as was all under counter cash in hand

Have disconnected the maf sensor and had a run around made a bit of difference but not much to be fair.

He thinks it could be the gear box and would need to take it to a specialist to have a look but that could be a costly repair money I haven't got.

Has anyone had this problem with there's before could it be a simple fix a cheaper fix or is it my gear box

Any help would be great

Oh and I'm a complete novice so please keep it simple

Many thanks

Chris

Brown · Mar 7, 2016

As the TD5 is all fly by wire and the engine speed is controlled by the ecu I'd be wondering about sensors. I understood the TD5 normally is programmed to lower the engine speed when you're changing gear so as to stop this sort of thing happening. I'd try sitting with the car stationary and getting the engine going with a steady lively hum and dipping the clutch just to see if it makes a difference to the engine revs.

Alternatively, do you have access to any diagnostic kit - Nanocom, Hawkeye, Lynx or anything similar? Might be revealing.

Chris mason 18 · Mar 7, 2016

Brown said:
As the TD5 is all fly by wire and the engine speed is controlled by the ecu I'd be wondering about sensors. I understood the TD5 normally is programmed to lower the engine speed when you're changing gear so as to stop this sort of thing happening. I'd try sitting with the car stationary and getting the engine going with a steady lively hum and dipping the clutch just to see if it makes a difference to the engine revs.

Alternatively, do you have access to any diagnostic kit - Nanocom, Hawkeye, Lynx or anything similar? Might be revealing.

No diagnostic kits I'm afraid had one couple weeks ago 1000s lights showed up so the guy at the garage reset them after we had done few miles he was gunna plug it back in to check

The car is a auto but only ever happens when it is coming up to the 30 mark and sometimes the 50

Brown · Mar 7, 2016

I'm sorry - I see it says auto in your post. I was thinking about my TD5 manual. In which case I'd be thinking very seriously about the electronics, as the gearbox and the engine management will be controlled by the ecu.

Chris mason 18 · Mar 7, 2016

Brown said:
I'm sorry - I see it says auto in your post. I was thinking about my TD5 manual. In which case I'd be thinking very seriously about the electronics, as the gearbox and the engine management will be controlled by the ecu.

Many thanks what electronics should I be looking at, is there any as a novice I can look at my self the bloke at the garage said he had a good look at the relay and the electronics he couldn't see anything that would course this my td5 has oil in loom problem bloke cleaned out plug with contact cleaner couple days ago as stopped running ever since the clean been starting fine could it just be the fuel injectors would this show up on diagnostic testing?

Brown · Mar 7, 2016

As I don't have an automatic this is a bit beyond my experience so I'm just guessing, but it seems to me that whatever sensors plug into the gearbox would be a start. It sounds like your man has just had a cursory look at the ECU, relays and the like and had a bit of a squirt round with electrical cleaner. I doubt if it would be a problem with injectors. Sounds like they're working only too well. Although the diagnostic code reader can show up injector faults and this could be the subject of a whole new debate, we'll leave that for now. The ECU will be getting signals from a variety of sensors on the engine and transmission, including but not limited to the crank position sensor, the sensor on the gearbox, the sensor that drives the speedo, the fuel temperature, the MAF, the sensor in the airbox, the one on the inlet manifold and a good few more. And these are all combined together by an algorithm that determines what the engine does. Another wild guess on my part has to do with the xyz switch on the gearbox, as I understand these are prone to failure because the aircon condensation drains onto them. However, that's as much as I know and I'll shut up now in the hope that someone more familiar with your model will come along.

Chris mason 18 · Mar 7, 2016

Brown said:
As I don't have an automatic this is a bit beyond my experience so I'm just guessing, but it seems to me that whatever sensors plug into the gearbox would be a start. It sounds like your man has just had a cursory look at the ECU, relays and the like and had a bit of a squirt round with electrical cleaner. I doubt if it would be a problem with injectors. Sounds like they're working only too well. Although the diagnostic code reader can show up injector faults and this could be the subject of a whole new debate, we'll leave that for now. The ECU will be getting signals from a variety of sensors on the engine and transmission, including but not limited to the crank position sensor, the sensor on the gearbox, the sensor that drives the speedo, the fuel temperature, the MAF, the sensor in the airbox, the one on the inlet manifold and a good few more. And these are all combined together by an algorithm that determines what the engine does. Another wild guess on my part has to do with the xyz switch on the gearbox, as I understand these are prone to failure because the aircon condensation drains onto them. However, that's as much as I know and I'll shut up now in the hope that someone more familiar with your model will come along.

Many thanks much appreciated

NeilB · Mar 8, 2016

As the gearbox changes gear based on pressure of the ATF I would check the oil level first. Follow the correct procedure, don't just pull the dipstick out and have a look. It may be that you are a little low and it takes a while for the pressure to build.

Chris mason 18 · Mar 14, 2016

After speaking to a auto transmission specialist he knows exactly what the problem is

And wait for it

£1450

Hole days labour
£100 in oil
Complete rebuild
And a new transfer box

Brown · Mar 14, 2016

Oh well, I suppose the advantage is that everything will be nice and new so won't need replacing again for a few years. Assuming you're intending to keep the car for a few years!

MJI · Mar 15, 2016

Chris mason 18 said:
After speaking to a auto transmission specialist he knows exactly what the problem is

And wait for it

£1450

Hole days labour
£100 in oil
Complete rebuild
And a new transfer box

Also now ask Ashcroft Transmissions

May be worth getting HD TC

Over revving

Chris mason 18

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Chris mason 18

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Chris mason 18

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Chris mason 18

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