idle non constant

[Xavier T]

Hi everybody
I have a little problem that appeared this spring.
My idle became non constant as it was perfect before.
This summer with hot temperatures the problem happened all the time and the engine could even sometimes stall.

With the winter coming, the temperature is getting lower and the problem seems disapear...

Any idea ?

Thanks a lot

[dapinky]

2 things which spring to mind (but there could be others!) - vacuum leak or temperature sensor....

..... easy to check both.

To check vacuum leak, let the engine run at idle and remove any of the vacuum pipes from the inlet plenum - if the idle stays the same, there was already a leak, but if it dips then rises before settling, then it was fine. If there is a leak, you need to find it and fix it by mending or replacing the offending pipe.

To check the coolant sensor, if you have elanscan it will tell you what the readings are, but if you haven't, then you can check the resistance values at 0deg and 100deg (place in ice water, then place in boiling water). I can't remember the values it should be, but it is somewhere on the forum!!!

Also, if you put the car into service mode does the idle settle? That mode takes all the engine sensors out of the system, so it is how you set the idle properly at 950rpm.

[Tuga2112]

my first thought was IAC valve, although they dont have an habbit of failing, they are one of those things that directly affects the idle.

how does the car operate when warm ? i mean the engine being warm. not the weather.

[Xavier T]

When the engine was warm i had the same problem of non constant idle.

[Xavier T]

Well, the problem has been solved

I had to pass the MOT and I failed it. The lambda wasn’t correct.
I changed the lambda oxygen sensor and il solved the emission problem but also the inconstant idle.