Cold start problem.

[audismart]

Hi chaps, hope you can help,
Engine 2.0 tfsi

On cold starts in the morning car starts but goes to 8k revs almost straight away, its as if there is a sensor telling the ecu that the car is warm when its cold, seems to be when its under 7 deg outside, car is struggling and missing when it happens, as soon as the car seems to be warming up it all settles down quite quickly and runs sweet as a nut.

I`m leaning towards a coolant temp sensor and got one on order but not sure?

Also could it be the 02 sensor on the exhaust? and which one pre or post cat?

its not pcv as newish, not coilpacks as new, not air intake temp sensor as new, Ive blasted the maf with electrical cleaner, but not wanting to chuck another £100 at it for it not to be the problem.

 

[Rideen]

Hi chaps, hope you can help,
Engine 2.0 tfsi

On cold starts in the morning car starts but goes to 8k revs almost straight away, its as if there is a sensor telling the ecu that the car is warm when its cold, seems to be when its under 7 deg outside, car is struggling and missing when it happens, as soon as the car seems to be warming up it all settles down quite quickly and runs sweet as a nut.

I`m leaning towards a coolant temp sensor and got one on order but not sure?

Also could it be the 02 sensor on the exhaust? and which one pre or post cat?

its not pcv as newish, not coilpacks as new, not air intake temp sensor as new, Ive blasted the maf with electrical cleaner, but not wanting to chuck another £100 at it for it not to be the problem.

I'm really hoping you've made a mistake there and that the car doesn't have self destructing wishes thus reaching 8k revs by itself on startup.

Do a VCDS scan, should tell you everything.

 

[Retroman]

Best get it plugged onto a diagnostic tool. Even the simplest OBD II tool will give a live reading of the coolant temperature being recorded. Your problem might be the coolant temperature sensor but best to pinpoint the problem and be sure. This sensor is a common fault on BMW Minis, where it results in difficult starting (the ECU thinks the coolant is immediately at 90C), coolant fans cutting in immediately and overheating warning lights on the dash.

When you say 8k do you mean 800 rpm i.e. the ECU is not raising the idle to the slightly higher cold rpm?

 

[audismart]

I'm really hoping you've made a mistake there and that the car doesn't have self destructing wishes thus reaching 8k revs by itself on startup.

Do a VCDS scan, should tell you everything.

Yeah my bad, 800rpm should be.
yeah no codes coming up on vcds.

 

[audismart]

Best get it plugged onto a diagnostic tool. Even the simplest OBD II tool will give a live reading of the coolant temperature being recorded. Your problem might be the coolant temperature sensor but best to pinpoint the problem and be sure. This sensor is a common fault on BMW Minis, where it results in difficult starting (the ECU thinks the coolant is immediately at 90C), coolant fans cutting in immediately and overheating warning lights on the dash.

When you say 8k do you mean 800 rpm i.e. the ECU is not raising the idle to the slightly higher cold rpm?

Yep exactly that, my bad meant to put 800rpm. When you say 8k do you mean 800 rpm i.e. the ECU is not raising the idle to the slightly higher cold rpm?

 

[audismart]

Bump
Driving me mad now.
New PCV
New camshaft sensor
New N80 valve
New coolant temp sensor
02 sensors post and pre.
had new plugs last year and fuel filter.

Fitting brake boost pipe with check valve tomorrow.
Just not confident that I will get an end to this.
Next will be carbon clean of the intake valves and new injectors.
Wonder if the HPFP might be on its way out?

 

[R222cet]

Ive noticed this with my S3 only does it now and again tho. It’s only just had a service last week and scanned, nothing found I’ll be watching this thread

 

[audismart]

Ive noticed this with my S3 only does it now and again tho. It’s only just had a service last week and scanned, nothing found I’ll be watching this thread

Mine does it as soon as the ambient temp drops to 4 deg on a cold morning, its as if there isn't enough fuel being dropped into the intake to feed the extra revs for cold start.

 

[R222cet]

It could be the temp I’ll keep my eye on it. What problems could it be causing ?