D2 TD5 throttle issue

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PurityVendetta

PurityVendetta

Member
Posts
48
Location
Shrewsbury UK
Hi everyone, I have noticed an odd problem with my normally very reliable 2000 Discovery 2 TD5 manual (no sunroof, no ACE). Okay, she's fairly high milage, 180k, but we'll maintained.
Recently I've noticed when changing gear there seems to be an intermittent fault. On pressing the clutch and releasing the throttle there is a lag or hesitance before the rpm drop off. Otherwise she seems as fit and healthy as ever. I've checked the clutch anti surge switch and it's power and ground and all seems well. I went on to check the MAF which, using a multimeter appears to be giving the correct output. I did check the MAF's power supply and ground too. I cleaned the MAP sensor and will check it's power, ground and output once I've found a pin out diagram as the copy of RAVE I have seems to be missing the page that has the appropriate schematic. I have checked the plugs into the ECU and there's no oil but this problem doesn't feel like the oil through the injector harness which I've had happen and replaced the harness. I also had the sticking wastegate thing and fixed it.
The fault is driving me nuts as I'm usually good at tracking things down and do all of my own work. I don't have a Hawkeye or Nanocom and have been trying to logically go through each component that might cause this. The pandemic and such has hit us pretty hard as I'm self employed so can't just load the parts cannon on this one. I absolutely love my Disco, so much that I'm fitting a replacement 1/3 chassis this summer when I've saved enough money. She does everything I've ever asked her to and has only let me down once in the 7 years I've owned her. She tows trailers, can fit a pair of full sized oxyacetylene bottles in the back and takes all the doggos in the back. What more could I want.
Any help or advice would be very much appreciated.
 
PurityVendetta said:
Hi everyone, I have noticed an odd problem with my normally very reliable 2000 Discovery 2 TD5 manual (no sunroof, no ACE). Okay, she's fairly high milage, 180k, but we'll maintained.
Recently I've noticed when changing gear there seems to be an intermittent fault. On pressing the clutch and releasing the throttle there is a lag or hesitance before the rpm drop off. Otherwise she seems as fit and healthy as ever. I've checked the clutch anti surge switch and it's power and ground and all seems well. I went on to check the MAF which, using a multimeter appears to be giving the correct output. I did check the MAF's power supply and ground too. I cleaned the MAP sensor and will check it's power, ground and output once I've found a pin out diagram as the copy of RAVE I have seems to be missing the page that has the appropriate schematic. I have checked the plugs into the ECU and there's no oil but this problem doesn't feel like the oil through the injector harness which I've had happen and replaced the harness. I also had the sticking wastegate thing and fixed it.
The fault is driving me nuts as I'm usually good at tracking things down and do all of my own work. I don't have a Hawkeye or Nanocom and have been trying to logically go through each component that might cause this. The pandemic and such has hit us pretty hard as I'm self employed so can't just load the parts cannon on this one. I absolutely love my Disco, so much that I'm fitting a replacement 1/3 chassis this summer when I've saved enough money. She does everything I've ever asked her to and has only let me down once in the 7 years I've owned her. She tows trailers, can fit a pair of full sized oxyacetylene bottles in the back and takes all the doggos in the back. What more could I want.
Any help or advice would be very much appreciated.
Click to expand...
Are you sure the clutch is disengaging as soon as it should?
If it stays momentarily engaged the wheels, through the gears etc could keep everything turning a tiny bit longer if the clutch is still engaged, i.e. as if you were using it for engine braking.
Maybe the clutch is sticky or there is a slight lack of fluid in the system, or a leak?
Just a thought.
 
Stanleysteamer said:
Are you sure the clutch is disengaging as soon as it should?
If it stays momentarily engaged the wheels, through the gears etc could keep everything turning a tiny bit longer if the clutch is still engaged, i.e. as if you were using it for engine braking.
Maybe the clutch is sticky or there is a slight lack of fluid in the system, or a leak?
Just a thought.
Click to expand...
Hi, thanks for the reply. No, the clutch isn't sticking and there's no fluid leak. It feels sometimes that there's a slight surge in the rpm's when changing up. It sot of feels like a mechanical throttle sticking but the TD5 being fly by wire somewhat rules this out. The accelerator pedal itself feels normal with no sticking on it's pivot. I might try to check the resistance on the throttle pots if I can identify the pin outs at the ECU or even drop the pedal unit itself.
 
PurityVendetta said:
Hi, thanks for the reply. No, the clutch isn't sticking and there's no fluid leak. It feels sometimes that there's a slight surge in the rpm's when changing up. It sot of feels like a mechanical throttle sticking but the TD5 being fly by wire somewhat rules this out. The accelerator pedal itself feels normal with no sticking on it's pivot. I might try to check the resistance on the throttle pots if I can identify the pin outs at the ECU or even drop the pedal unit itself.
Click to expand...
The pots are renowned for being troublesome.
 
PurityVendetta said:
Hi, thanks for the reply. No, the clutch isn't sticking and there's no fluid leak. It feels sometimes that there's a slight surge in the rpm's when changing up. It sot of feels like a mechanical throttle sticking but the TD5 being fly by wire somewhat rules this out. The accelerator pedal itself feels normal with no sticking on it's pivot. I might try to check the resistance on the throttle pots if I can identify the pin outs at the ECU or even drop the pedal unit itself.
Click to expand...
I think I've got the same problem, I tried replacing the clutch switch which helped for a while, but noticed its come back recently.
 
PurityVendetta said:
I've checked the clutch anti surge switch and it's power and ground and all seems well.
Click to expand...
The only certain way to check that switch is to read the input to the ECU with diagnostic tool, what do you mean by "it's power and ground and all seems well" cos once the clutch is depressed the switch should close to ground and no power is supposed to be there, the description of this switch in the WSM is wrong
 
sierrafery said:
The only certain way to check that switch is to read the input to the ECU with diagnostic tool, what do you mean by "it's power and ground and all seems well" cos once the clutch is depressed the switch should close to ground and no power is supposed to be there, the description of this switch in the WSM is wrong
Click to expand...
The ECU appears to output a voltage to the switch, I'm measuring as 11v and the switch appears to close and ground this output when the clutch is depressed.
When you say the workshop manual is incorrect, what exactly is wrong? I've been using a downloaded 2001 version of RAVE. I think the manual might have the switch states v. the clutch pedal position the wrong way around but there has to be a signal level voltage for the ECU to read when the switch is open or closed to ground surely?
Unfortunately I don't have access to a diagnostic unit and can't afford to buy one right now. I'll have to check one how much the local garage charges to clear any codes, take the car for a drive and see what codes crop up if any. We've just had to pay a £2k vets bill are just a bit hard up at the moment.
 
Last edited:
Defender91 said:
I think I've got the same problem, I tried replacing the clutch switch which helped for a while, but noticed its come back recently.
Click to expand...
Hi, a few people seem to have had the same problem as we're having judging by posts on the interweb but none of them seem to end in a successful fix. The threads just seem to peter out and, I assume the person fixed the issue but didn't bother to post a solution. It's really frustrating but if I do fix it I'll post whatever I find out.
 
sierrafery said:
The only certain way to check that switch is to read the input to the ECU with diagnostic tool, what do you mean by "it's power and ground and all seems well" cos once the clutch is depressed the switch should close to ground and no power is supposed to be there, the description of this switch in the WSM is wrong
Click to expand...
I've just read through a post you replied to concerning the same problem someone else was experiencing. The WSM says that battery voltage is delivered to the switch from pin 35 on the ECU. I'm measuring something around 11v on the Black with white tracer wire which seems a little down from my battery voltage which is 12.4 with the ignition on but the engine not running. I did check the earth with my fluke but I have a mind to check this with a load (an incandescent bulb continuity tester) as I've come across issues where a multimeter checks a poor earth out as okay due to it's huge internal impedance making it very sensitive. I'm also going to disconnect the ECU multiplug and check the cabling back to the ECU. This fault on my car feels a little intermittent which I suspect could be something like a poor earth or connection. The plug to the switch does look very clean and corrosion free. And so do both ECU multiplug as I remember cleaning them meticulously when I replaced the injector loom.
I'll post any results after I've fiddled around in the morning. I hope this will get to the bottom of this but your replies on the other thread were very helpful in understanding the functioning of the anti surge switch circuit.
 
The description in the WSM for the clutch switch is:
Input/Output
The clutch switch receives battery voltage from the BCU. With the clutch pedal in the rest position the switch is closed,
allowing battery voltage to pin 35 of the ECM connector C0658. When the clutch pedal is pressed the switch contacts
open, interrupting the power supply to the ECM. The ECM receives 0 Volts.
which is wrong cos the diagram is correct and the switch is N/O and closes to earth on clutch request as it's shown in this edited part of the diagram, exclude the part from the red square which is for autos and see the path only for manual, i've seen cases when the switch closed and passed a multimeter test but it had some internal resistance and didnt work for the management so better rule out the switch with a new one to be 100% sure it's OK
Clutch switch circuit.jpg
 
tilly2 said:
Which side of Shrewsbury are you ? Im near Newport and have a Nanocom.
Click to expand...
Hi, I'm up near Shawbury but would have no problem driving over to you if I could use your Nanocom. I'd be very grateful and of course buy you a beer for the help. I'm going to try a few things today and make sure I've eliminated any simple issues. I could pm you to arrange a visit.
Once again, thank you for your very kind offer. I normally work on vintage and classic motorcycles so working with relatively complex engine management systems isn't the norm for me.
 
Okay, I'm pretty sure I have the problem isolated. After much fiddling and trial and error it appears to be an intermittent fault with the infamous clutch switch. The thing that was throwing me was the intermittent nature of the symptoms. In the end I shorted the switch and the throttle issue was gone on a test drive. I have a new switch ordered that should be here tomorrow or Saturday.
As a side note, the switch tested fine using my Fluke 115 dmm but as the fault only appeared possibly once in maybe ten depressions of the pedal it was awkward to reproduce. I'm going to try an analogue AVO 8 tomorrow to see if I can generate a detectable fault using the AVO's higher range as I've sometimes found that an AVO can give a better reading in this kind of situation.
Anyway, I'll get the new switch fitted as soon as I get it and, all being well, close up this thread with a satisfactory conclusion.
Thanks for all the help and advice everyone.
 
Okay, I'm going to wrap this one up for now. Fitted a new OEM switch today and the issue is fixed. The car is behaving just as it should and running well. As Griff said, if you get everything ready and are nimble during the swap you might get away without having to bleed the system. I'd always advise that you check you can actually undo the bleed nipple before you start. All in all an annoying little issue but £30 odd and some fiddling about to make sure I wasn't just loading the parts cannon without being sure of the cause of the fault. My day job is working with vintage and classic motorcycles so all this fly by wire electronic fuel injection took me a little while to get my head around. I'd say to anyone who's experiencing this problem to simply unplug the switch and short the pins of the connector. Take the car for a short drive and if the rpm's behave properly during gear changes you're good to go ahead and order the part. One thing to note is that when I measured the voltage supplied to the switch it's not battery voltage it's about 11.6 volts (13.4v at the battery terminals).
I'd like to thank everyone who stepped up with suggestions and offers of help. I know this will sound a bit silly but our Disco is more than just a car, she's part of the family. For other reasons we've had a pretty rough week and we needed to get to places in an emergency, obviously our Disco got us there no problem as usual.
 
Landmark2 said:
Glad you've sorted it and given the end result for future "searchers"
Speak soon,
Griff
Click to expand...
Thanks Griff. I really find those threads that just stop short with no conclusion or solution frustrating.
As an aside, our boy Rocky is doing well so far. We have put him on antibiotics as a precaution and our girl Bella isn't showing any symptoms of KC. We're still a shell shocked over the events of the last weekend but I'll be in touch when I think the situation here is safe and under control.
 
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