A4 2.0TFSI very rough ildle/Misfire on cold starts - please help

[gordonowusu]

Hello Guys,
I Have been having troubles with my 2008 B7 2.0T. Noticed my car idles very rough when I start for the first time i.e cold start, the engine will vibrate very bad as if it is running only on 2 cylinders. the check engine light will start flashing for about 10 seconds before it stays solid. but after 2 minutes it will be back to normal and run fine until another cold start start. I scanned and had the following codes.

1. coolant temperature sensor - Sporadic
2. Rear heater core

I have replaced the coolant temperature sensor at rear of engine. Replaced spark plugs with new ones. replaced all 4 coils with brand new. this has made no difference. the problem is still there.

I unplugged the MAF before starting the car this morning. the engine idled fine without blinking check engine light. the vibration/misfire was gone. I waited for the engine to cool and i plugged back the MAF. the problem was back. took it off again and waited for the engine to cool. started it and there was no misfire or vibration.

I drove the car for about 10 minutes and was ok but just a slight change in engine sound probably due to the ECU running on default values due to the unplugged MAF.


I want to replace the MAF but I want to be sure before spending another cash without solving the problem. Am sure the MAF may be faulty since the rough idle vanished when I unplugged it.

I need your advice before making the next move by replacing the MAF.

Thanks,

Gordon.

[Doctle Odd]

The MAF sensor must be genuine so have a look at yours first. Aftermarket ones tend to be rubbish and they don't always generate a fault code

[gordonowusu]

Thanks for the reply. Will have a look at mine. how do tell if its genuine or an aftermarket one?

[Doctle Odd]

There should be an Audi logo and part number on a genuine one

[gordonowusu]

It has the Audi logo with part number 0SD 906 461. its is made by hitachi.

[MrBigglesworth]

Have you got VCDS - might be worth scanning for error codes or doing some logs to see how the MAF responds?

[gordonowusu]

Update

Thanks for your help guys. I got a proper VCDS cable and pointed out to cylinder #1 injector. i replaced with a second hand unit a friend (mechanic) gave me. cleared codes and car has been working like a dream.

thanks you all.