Searching idle in neutral
Discussion
Edit: title should read: searching revs at idle/neutral
I know idle problems seem to have around 1000 possible causes, but I may be able to rule some out at least.
My car seems to idle normally when it's first started, however once I'm on the move if I dip the clutch or if I come to a stop and put it in neutral my revs seem to rise and fall.
I had a similar problem before I had the car serviced (back in Sept time), but after that it was perfect again, so I'm guessing whatever was done at the service sorted it.
I've tried cleaning the stepper motor as a starting point, but that doesn't seem to have solved anything.
I thought it may have been something to do with the speed sensor, but wouldn't that only occur when I'm stationary?
Any help would be appreciated!
I know idle problems seem to have around 1000 possible causes, but I may be able to rule some out at least.
My car seems to idle normally when it's first started, however once I'm on the move if I dip the clutch or if I come to a stop and put it in neutral my revs seem to rise and fall.
I had a similar problem before I had the car serviced (back in Sept time), but after that it was perfect again, so I'm guessing whatever was done at the service sorted it.
I've tried cleaning the stepper motor as a starting point, but that doesn't seem to have solved anything.
I thought it may have been something to do with the speed sensor, but wouldn't that only occur when I'm stationary?
Any help would be appreciated!
I had the same problem. Changed the coolant sensor, but made no difference. Cleaned stepper motor but that made no difference. Then broke the stepper motor by mistake! Put a new one in, cleaned the idle control valve chamber and plenum and put it all back together, checked for leaks, reset the ECU and it was all fine. Idled perfectly.
)zed4 said:
Harrytsg said:
I had exactly the same symptoms as you describe, and (with the exception of changing the coolant sensor) did exactly the same as zed4 described (including breaking mine) and it was cured.
Breaking the old part is a very critical piece of the process! 
It may only be coincedental but I was experiencing surging idle and if i dipped the clutch as you are, cleaned the stepper and the plenum and it was intermittant, then my fuel pump and ecu relay packed up, replaced the relays and touch wood it has been fine since. It had something to do with the lamda probe heating and the ecu over compensating (i think).
V8OW said:
Thanks all.
I'm not too concerned, but as the car is for sale I'm trying to sort a few niggles first.
How much is a replacement stepper?
I paid £90 for a genuine Lucas part, with a Land Rover part number stuck on the box, from a small Land Rover specialist near me (Brooklyn 4x4). I think they'd had it in stock for a long time and wanted to shift it. Just ring around, prices vary. I'm not too concerned, but as the car is for sale I'm trying to sort a few niggles first.
How much is a replacement stepper?
Restting the ECU is simply done by unplugging it from the loom- but its not a fix, it just resets the fueling and clears any fault codes, it does nothing for the stepper control. To get a stable idle you need:
1) A clean stepper, housing and no air leaks
2) A throttle pot thats correctly set up. An over high setting stops idle mode.
3) A base idle thats been set up correctly.
4) No speed signal to the ECU to show the car is not moving.
The speed signal is generated by a box of electronics under the dash, and it has 2 input signals, one ground and one from the diff sensor. It should start to generate a speed signal as a signal from the diff sensor is created as the car moves forward, but if the grounding is poor a very small stray signal on the earth wiring causes the unit to produce a false speed signal, so the ECU thinks the car is moving. This causes the ECU to hold the idle randomly high. You need ECU dignostics to physically see if this signal is present when the car is stationary, or to start with simply try and clean all the earth straps- apparently there is one near a front wing that is prone to corrosion (?).
1) A clean stepper, housing and no air leaks
2) A throttle pot thats correctly set up. An over high setting stops idle mode.
3) A base idle thats been set up correctly.
4) No speed signal to the ECU to show the car is not moving.
The speed signal is generated by a box of electronics under the dash, and it has 2 input signals, one ground and one from the diff sensor. It should start to generate a speed signal as a signal from the diff sensor is created as the car moves forward, but if the grounding is poor a very small stray signal on the earth wiring causes the unit to produce a false speed signal, so the ECU thinks the car is moving. This causes the ECU to hold the idle randomly high. You need ECU dignostics to physically see if this signal is present when the car is stationary, or to start with simply try and clean all the earth straps- apparently there is one near a front wing that is prone to corrosion (?).
blitzracing said:
Restting the ECU is simply done by unplugging it from the loom- but its not a fix, it just resets the fueling and clears any fault codes, it does nothing for the stepper control. To get a stable idle you need:
1) A clean stepper, housing and no air leaks
2) A throttle pot thats correctly set up. An over high setting stops idle mode.
3) A base idle thats been set up correctly.
4) No speed signal to the ECU to show the car is not moving.
The speed signal is generated by a box of electronics under the dash, and it has 2 input signals, one ground and one from the diff sensor. It should start to generate a speed signal as a signal from the diff sensor is created as the car moves forward, but if the grounding is poor a very small stray signal on the earth wiring causes the unit to produce a false speed signal, so the ECU thinks the car is moving. This causes the ECU to hold the idle randomly high. You need ECU dignostics to physically see if this signal is present when the car is stationary, or to start with simply try and clean all the earth straps- apparently there is one near a front wing that is prone to corrosion (?).
OK, thanks. 1) A clean stepper, housing and no air leaks
2) A throttle pot thats correctly set up. An over high setting stops idle mode.
3) A base idle thats been set up correctly.
4) No speed signal to the ECU to show the car is not moving.
The speed signal is generated by a box of electronics under the dash, and it has 2 input signals, one ground and one from the diff sensor. It should start to generate a speed signal as a signal from the diff sensor is created as the car moves forward, but if the grounding is poor a very small stray signal on the earth wiring causes the unit to produce a false speed signal, so the ECU thinks the car is moving. This causes the ECU to hold the idle randomly high. You need ECU dignostics to physically see if this signal is present when the car is stationary, or to start with simply try and clean all the earth straps- apparently there is one near a front wing that is prone to corrosion (?).
Have cleaned it and will see how it is on the way home. If not I will be seeing my local TVR specialist.
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