Speedo calibration unit
Discussion
The more I found out about the ECU, the more that it seems can go wrong with the idle control- Im not surprised that the idle control software has been tweaked many times. You have lots of inputs that lift the idle.
ECU inputs:
Throttle pot.
Speed pulse.
Air Con.
Heated screen (Range Rover).
Engine temp (cold reading).
Mechanically:
Stick stepper motor operation
Mixture control- ie air leaks or wrong initial mixture due to a wrong sensor input like AFM.
Ignition timing and Air bypass valve setting- the timing has a huge affect on the RPM at idle, and consequentially the amount of air needed to keep the idle stable.
Potential misfires or general poor running.
At least with diagnostics we can now get if the ECU is in idle mode and more importantly what the target idle RPM is- as this changes with the ECU sensor inputs, so at least you can tell if its the ECU holding the idle up, or something mechanical.
ECU inputs:
Throttle pot.
Speed pulse.
Air Con.
Heated screen (Range Rover).
Engine temp (cold reading).
Mechanically:
Stick stepper motor operation
Mixture control- ie air leaks or wrong initial mixture due to a wrong sensor input like AFM.
Ignition timing and Air bypass valve setting- the timing has a huge affect on the RPM at idle, and consequentially the amount of air needed to keep the idle stable.
Potential misfires or general poor running.
At least with diagnostics we can now get if the ECU is in idle mode and more importantly what the target idle RPM is- as this changes with the ECU sensor inputs, so at least you can tell if its the ECU holding the idle up, or something mechanical.
blitzracing said:
The more I found out about the ECU, the more that it seems can go wrong with the idle control- Im not surprised that the idle control software has been tweaked many times. You have lots of inputs that lift the idle.
ECU inputs:
Throttle pot.
Speed pulse.
Air Con.
Heated screen (Range Rover).
Engine temp (cold reading).
Mechanically:
Stick stepper motor operation
Mixture control- ie air leaks or wrong initial mixture due to a wrong sensor input like AFM.
Ignition timing and Air bypass valve setting- the timing has a huge affect on the RPM at idle, and consequentially the amount of air needed to keep the idle stable.
Potential misfires or general poor running.
At least with diagnostics we can now get if the ECU is in idle mode and more importantly what the target idle RPM is- as this changes with the ECU sensor inputs, so at least you can tell if its the ECU holding the idle up, or something mechanical.
Good summary.ECU inputs:
Throttle pot.
Speed pulse.
Air Con.
Heated screen (Range Rover).
Engine temp (cold reading).
Mechanically:
Stick stepper motor operation
Mixture control- ie air leaks or wrong initial mixture due to a wrong sensor input like AFM.
Ignition timing and Air bypass valve setting- the timing has a huge affect on the RPM at idle, and consequentially the amount of air needed to keep the idle stable.
Potential misfires or general poor running.
At least with diagnostics we can now get if the ECU is in idle mode and more importantly what the target idle RPM is- as this changes with the ECU sensor inputs, so at least you can tell if its the ECU holding the idle up, or something mechanical.
Methinks, By stick stepper means a lazy stepper, communicating lazily with lazy ECU. Mine is lazy on idle and slowing down when engine is not fully warmed up. When hot 70-85 C it's ok.
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