Low idle when cold outside temp (-3°C or 26°F)

[D.Martijn]

Hey everyone,

I noticed today as it's getting colder (-3°C) my 325ix had a pretty low idle just above 500rpm, when I turned on my lights as it was already dark outside I could notice them reducing brightness and then intensifying over and over again.. It didn't stall though.. As I arrived back home, the car idled like usual.

Anyone that has an idea what the problem could be?

Thanks :)

[dnguyen1963]

On cold days, I would wait until the temp needle pops into the normal reading range before I turn on any electronics. On a really cold day (below -9C), the tach needle would move up and down from about 500 to 900 rpm until the engine is warmed up. It has been doing this forever during the winter months. Once the engine is warm, everything behaves as normal.

[D.Martijn]

On cold days, I would wait until the temp needle pops into the normal reading range before I turn on any electronics. On a really cold day (below -9C), the tach needle would move up and down from about 500 to 900 rpm until the engine is warmed up. It has been doing this forever during the winter months. Once the engine is warm, everything behaves as normal.

I usually wait a minute before pulling out, once I'm on the road I make sure not to push the engine till it's warmed up.

Could it be the blue temperature sensor acting up? If I'm right this sensor tells the ECU what temp the engine is so the ECU can adjust the fuel delivery.

[dnguyen1963]

I think it is the oil we used in our car. 15W40 is quite thick when the temperature drops that far. It takes a few minutes to distribute the oil evenly.

[digger]

ICV working properly? it should maintain slighty faster idle when cold

[dnguyen1963]

ICV working properly? it should maintain slighty faster idle when cold

I have not checked. The ICV works fine when the temp is above 15F. I generally park the car on days when the temp drops too far.

[squidmaster]

Materials slightly expand or contract in temperature differences, wouldn't hurt to clean out the icv. Using a lower weight oil helps sometimes, too.

[D.Martijn]

I think it is the oil we used in our car. 15W40 is quite thick when the temperature drops that far. It takes a few minutes to distribute the oil evenly.

Been using 10W40 oil which is a tad thinner than 15W40 when cold

ICV working properly? it should maintain slighty faster idle when cold

Materials slightly expand or contract in temperature differences, wouldn't hurt to clean out the icv. Using a lower weight oil helps sometimes, too.

Haven't checked the ICV since I get home quite late, I'll check it this weekend. I'll report back :)

[squidmaster]

Sorry, didn't notice you using 10w40. While that shouldn't be too bad for cold weather, I noticed a stark difference in startup and idle while very cold using anything over 10w30, with 20w50 making it worrying difficult to start on some below 0 mornings.

[dnguyen1963]

The reason I don't use anything thinner than 15W40 is that the car does not take very long to get up to temp (yes, 10W30 can give you an easier starting) and, when the engine is at operating temp, lower viscosity oil does not offer adequate protection.

[D.Martijn]

Today I cleaned my ICV. When loosening the hose clamps I noticed that the little elbow that's fitted on the throttle body was loose.


I decided to remove it and seal it up again with sealant.

I'll report if this fixes my idling

I also noted that the little tube has some small cracks in it, so I've ordered a new one from BMW.

[dnguyen1963]

Very common problem.

[D.Martijn]

Problem seems to be fixed.
By sealing the little elbow and cleaning out the ICV.