Issues with K12 issuesm revs when cold

Hi,

In October I bought my daughter her first car which is a 2003 Micra 1.2S. With the help of posts from this club I have solved failed boot button, interior light and airbag warning light issues so thank you. However, my biggest headache is still not solved. Two weeks after purchase it developed issues on idle when cold with the revs rising and falling for a few minutes and then clearing. A local independent garage cleaned a reset the throttle body and for two weeks all was OK. Since then the problem has returned but isn't exactly the same. The car starts and runs (when warm) without issues apart from a tendency to lurch at low speed in any gear but if you press the accelerator it is fine. Performance and economy are good. When cold, after about two minutes the revs can rise to 1500 and fall to 600 rpm and although the car keeps running, there is a lot of smoke from the exhaust and the car runs rich. After a few minutes, and when the cold light has gone out, it clears, idles at 800 rpm and doesn't smoke. It has been back to the garage and they wired it up and although it doesn't show any fault codes, they see that the fuel management is erratic when cold and actually not 100% when warm. We are awaiting a final diagnosis but it is apparently pointing towards a main/engine ECU issue. If it is this then it looks like I have the following options:

1. Replace with a new one from Nissan at £560 ex VAT plus £105/r to fit and reprogram.
2. Buy a second hand one and try and get it reprogrammed
3. Get the old one fixed (but if they can't see an obvious fault I have been told that they won't be able to fix it)

I have taken some video bit no idea how to upload these.

My apologies for the long (first) post but does anyone have any suggestions please?
 

John_D

Club Member
Radio Code Guru
While it's normal for the ECU to modify the tick over revs to around 1.5K revs when the engine is cold it usually drops back to the 'correct' 1K revs once the 'cold engine' light goes out. However one day last week I found that even though the engine had warmed up and a stop to briefly shop had been done the engine revs at tick over remained at 1.5K revs. Looking for a possible cause I turned the aircon off and immediately the tick over revs dropped back to 1K. Turning the aircon straight back on still kept the tick over at the normal value......... Seems like some sort of ECU glitch associated with starting the car at sub zero temperatures with the aircon in the on position?:confused: (I had left it on the previous evening when using it to prevent interior glass misting).
 
I would be looking at the throttle body maybe giving it a good clean and cleaning the air flow meter as that could cause over fueling ? A faulty water temp sensor could also cause rich running on cold start. I have only had my k12 for a short time but this is where i would start with most modern cars.
 
I would be looking at the throttle body maybe giving it a good clean and cleaning the air flow meter as that could cause over fueling ? A faulty water temp sensor could also cause rich running on cold start. I have only had my k12 for a short time but this is where i would start with most modern cars.
 
When symptoms first occurred the throttle body was cleaned and for two weeks the car ran OK k before issues returned.

Would a faulty water temperature sensor cause temporary rich running for a short period about 2-3 minutes after cold start or during the whole cold running period?

Could this also cause the car to be a bit jerky at low revs in each gear when it is isn't pulling?
 
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