Hello all, newbie to the forum and in need of dire help

I'm in need of some guidance here. I have a W203 2004 C180 Kompressor which was sitting idle in my garage for nearly 6 months (didn't need the car). Last week, I took the car to a garage to get the MOT and full service done again.

MOT Fail - As expected the car had a long list of faults and I agreed with the garage to get it all done. I had the check engine light on when driving to the garage.

One of the faults was the blowing exhaust, this was thought to be the cause of high emissions at the first MOT attempt. They had it repaired and to their surprise and mine emissions were still high. They advised that there might be some oil in the exhaust and emissions are caused by the oil burning out. They asked me to take the car away for the weekend and keep the engine running/drive it in low gears which I did for 3 days. The check engine light came up again while the engine was running and it was P0171 - System too lean (Bank 1). I cleared the error but came up again when the engine was left running for a while - this doesn't occur when I drive the car.

I informed the garage guys about the error code and they agreed to look into it. They had the car for 5 more days and came back to me saying they have done everything they can and the emissions are still high. From their checks MAS, CAT, Lambda sensor all are okay.

I wonder if this is caused because I've been driving around with a blown exhaust and the ECU has learned/adapted to it. Is there a way to reset the ECU completely (including Fuel trim / LTFT)

Any help on this topic would be highly appreciated, I am just running out of time, patience and money. I already spent £900+ on this car. I just don't know what to do now.

VIN: WDC2030462R164854

Emission readings; First
Engine speed: 2314rpm
CO: 3.90%
HC: 227ppm
Lambda: 0.89

Emission readings; Latest
Engine speed: 2356rpm
CO: 3.93%
HC: 278ppm
Lambda: 0.88

 

Check engine symbol came up the other day & engine a little rough,
Suspected ignition (misfire) but could not find a fault.
Got a code reader - showed "P0171" - "lean fuel mixture".
Spoke to retired bus driver / mechanic mate - suggested fuel filler cap seal faulty ?
Opened filler cap, no obvious failure,closed - FAULT GONE !! and stayed gone .
Cheapest repair ever = €0.00.
Doesn't get much better than that.

 

did you check for vacuum leaks? possibly off the breather to the intake pipe?