Limey
Member Since: 18 Oct 2013
Location: Northern Italy
Posts: 193
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I wonder if anybody can help me with this?
Firstly, no check engine light. So I'm probably not in a position to get error codes read.
Recently, I've had a new clutch (including DM flywheel fitted) all valeo parts.
Now when I'm driving at a steady speed it doesn't seem to be responding to the accelerator pedal correctly. The first quarter inch of travel seems to cause nothing to happen, and then it suddenly kicks in with a quarter inch's worth of acceleration instantly. Which of course makes it snatchy. It's a new problem, which wasn't there before the clutch job. Initially I'd though that the new dm flywheel with stiff springs was just something to get used to, but having done a 5 hour trip at the weekend, I had more time to feel exactly what was going on, and can now see it's something more.
Looking at other threads it seems like if the throttle potentiometer fails, that the throttle response stops working completely? Anybody had anything similar? I'm sick of the Landie living in workshops, and going broke paying for repair after repair, so it might be time for me to try and swap a sensor myself, if that's what it is. But as I say, no check engine light has come on.
I'd really be appreciative of any input.
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16th Jun 2014 8:00am |
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blackwolf
Member Since: 03 Nov 2009
Location: South West England
Posts: 17484
 
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I had a throttle pot failure on my Td5 Disco2 and the symptoms were quite similar to what you describe.
In effect there was a position of the pedal when the engine would drop back to tickover, press it further and it would be back where it should be. So if you gently and progressively revved the engine the revs would build up, drop off completely, then pick back up where they should be.
This defect would log a fault in the ECU but would not cause the MIL to illuminate unless a number of faults were received in a short time, ie pumping the pedal up and down would cause the MIL to come on and the vehicle to enter limp mode. The MIL and limp mode could be cleared by cycling the ignition (and I became quite adept at knocking it into neutral, turning the engine off and restarting it, without stopping the vehicle, but perhaps I shouldn't admit to that)! I seem to remember that the transient faults also disappeared from the fault log when the engine was stopped (but I may be wrong on that), but is certainly took me a while to diagnose it. A new throttle pot and pedal assembly completely cured it.
Changing the throttle pot on a Disco is a horrid job unless you have a competent mutant infant with tiny hands and unnaturally long arms do it for you, but I believe that it is quite easy on a Defender. Might well be worth a try if you can't get a fault read-out.
You are probably aware that there are three seperate tracks on the throttle pot (in effect three seperate pots) on later vehicles (only two on early ones) and the position reading from all three (or from both on early ones) is compared by the ECU for sanity. As you press the pedal one decreases from 12V towards 0V, one increases from 0V to 12V, and the readings from these summed should always equal 12V. The later ones had the third track added for extra reliability and I can't remember what it does. If there is an irregularity, usually caused by dirct or abrasion on the pot track, it should be detected, but the ECU can't always determine what the position of the pedal actually is so will drop to tickover in certain circumstances.
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16th Jun 2014 8:38am |
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