my 97 540ia starts rough when cold outside but great when warm outside.

[noahtheviking]

My battery is good and air intake temp sensor has been replaced. Actually I have tried two just in case. I don't get it I have no codes and the starting gets worse and rougher the colder it gets. but if its 60+ car is great. Yes again the battery is fine. mass air meter is also new.

[purplecty]

My battery is good and air intake temp sensor has been replaced. Actually I have tried two just in case. I don't get it I have no codes and the starting gets worse and rougher the colder it gets. but if its 60+ car is great. Yes again the battery is fine. mass air meter is also new.

Sounds like it's time to do all the intake gaskets...

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[noahtheviking]

those have been done as well. no vacuum leaks at all.

[jicaino]

Coils? have those been replaced? Plugs? coil boots? the more strain on old components, the more evident something needs replacing. Also if you could read the exterior temp before a cold start it would be useful to know if it's real (more or less accurate but real world connected, instead of -48°C like all of those when they go bad) or not. I believe the DME uses that for cold triggering enrichment.

[purplecty]

those have been done as well. no vacuum leaks at all.

Does that include the front and rear gasket along with the throttle body gasket?

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[edjack]

Might be the coolant temp sensor. Check coolant temp with test 7 when the engine is cold. It should agree with the ambient temp reading.

[noahtheviking]

all plugs and coils have been replaced along with coolant temp sensor i will check test 7 thank you. yes all gaskets replaced. any other suggestions?

[Santaclaus4]

You haven't given out enough information to warrant a trouble shooting response.
What do you mean by it starts rough? Like a cylinder isn't firing at all? Like they are all miss firing randomly?
You mention the battery is good. Does that mean the starter spins slow and you don't know why?
It's like playing a game of "whack-a-mole". Everyone has to keep guessing what's next.
If you could please give out more information it would be helpful.

[66.cobra]

How do you know there are no vacuum leaks? Did you use a smoke machine to test?

[JimLev]

How's your idle air controller, ever cleaned or replaced it?

[jicaino]

How's your idle air controller, ever cleaned or replaced it?

I think we have a winner here.

[noahtheviking]

thank you for all the replies and help the problem was a dying battery cell. I had the correct voltage so I assumed everything there was ok but nope woooooops! Sometimes its the simple things that are too easily looked over.