Idle is rough

[MikiH]

Hi
Hope someone can help.
My Micra has developed a nasty habit of running roughly/judder when I am at idle. It sits at about 500 rpm (warm) and is smooth but if I turn on any electrical load it tries to idle faster and shakes.
I recently fitted a new thermostat DIY and splashed a deal of water about flushing the radiator and my mot garage fitted a new sump and did the oil and filter.
Is this a throttle relearn thing?
Miki

 

[David B Gregory]

500rpm seems low. I've currently got 2 K12 Micras.. one is old with 147k on it... one is a 2010 with only 37k on it, and they both idle at around 750. Mine drops a bit when the alternator is under load (lights, rear screen heater, or air con), but only 50rpm or so, and only for a short while until the ECU or whatever evens it out.

I reckon your idle speed is too low, and when you load the alternator it's dipping even lower.

Idle control valve woudl be my main suspect.

 

[MikiH]

500rpm seems low. I've currently got 2 K12 Micras.. one is old with 147k on it... one is a 2010 with only 37k on it, and they both idle at around 750. Mine drops a bit when the alternator is under load (lights, rear screen heater, or air con), but only 50rpm or so, and only for a short while until the ECU or whatever evens it out.

I reckon your idle speed is too low, and when you load the alternator it's dipping even lower.

Idle control valve woudl be my main suspect. How old is your Micra? Some actually have an idle speed adjustment next to the idle control valve... some are controlled by a stepper motor. If the former, you can adjust it with an alan key.. if the latter, it needs doing via OBD.

It coudl be the idle valve faulty as well. Check all connections too as it's had a good soaking by the sound of it.

Hi
Thanks for replying.
My Micra is 2006 with 105,000 miles.
I underestimated the idle speed a bit, it is probably more like 600.
It is just a bit of a pain having had 2 things done, so which is the one that upset things? I was thinking that if the mechanic who did the dump disconnected the battery could that do it?
I have a decent independent Nissan garage in Lincoln, perhaps a visit to them.

 

[David B Gregory]

"if the mechanic who did the dump disconnected the battery could that do it? "

I can't see how that could do it, no. Maybe someone else on here knows more than I do, but I can't imagine why that should do it. I've dosconnected my battery loads of times to do stuff... never been an issue.

 

[MikiH]

Thanks again