# Help! Weird combo of errors: Brake Servo, Misfiring and System rich at idle!



## neofyt05 (Jul 29, 2009)

Hello everyone,

I'm having problems with my car and I really don't understand why. 

About my car:
White Golf GT TSI 90KW DSG.
I had the car since new (11/2009) and the car was running fine until I moved from Cyprus to the UK (and brought it with me) about 5 months ago. Been sitting for 8 months before being shipped and has covered 7k miles since.
The car has 31K miles has been serviced recently with new sparks (NGK), fuel and air filter (OEM), longlife Oil. 100% stock.

The problems:

Defect brake servo warning and chime while accelerating from standstill even though I can't see any problems. Very intermittent. Will go away after a mile. Garage checked everything and there are no problems. No code stored.
Code P2188: System too rich at idle. Happened about 2 months ago and gave me a CEL at start up. No other symptoms. Garage checked lambda values and found no issues.
Code P0303: Misfire Cylinder 3. Happened just once 3 days ago. It was a cold morning and I started the car. The car was shaking a bit but it does it quite often for a few seconds when I start the engine cold. I opened the door and the interior lights would tremble the engine then started misfiring giving me flashing CEL. I turned off the engine. Started the engine (with door closed) and everything went back to normal. The stored code disappeared from the memory on it's own after 15 miles.


Ok now the weird bit.
I only get these issues after filling the car with "supermarket" fuel (Sainsbury's) and I get them at the same time.
It happened 3 times in the last 5 months and always 2-3 days after filling with supermarket fuel (and washing the car). 

I always freak out and go to a garage they check everything and tell me "don't use cheap fuel" I go fill up with Shell VPower and then regular unleaded (Esso or Shell only). 
The car runs perfectly as long as I stick to premium branded fuel.

This time the car was driving without any problems at all for 2 months. Then I filled up with cheap fuel and got the misfire after 2 days. Then I bought a dose of Redex, the day after I got defect brake servo and pending P2188.

It seems unlikely that it's a coincidence. I can see how misfire and running rich are related but how is the brake booster related?
Could it be the battery messing with the ECU?

Please help me diagnose this. I'm having trouble with money at the moment and I can't do any repairs myself. 
Any help would be greatly appreciated.


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