Hello everyone, danish guy here!

I have a Skoda Octavia TSI 1.8L, 4 cylinder, 160hp with a manual. Have gone 200K km and is from 2008.

I've had the code P0171 for quite some time: 'System too lean bank 1'.

I have cleaned the MAF-sensor and checked for vac-leaks. About 90% sure it's not a vacuum leak.

I really want to keep the expenses as low as possible, so before I advance with the repairs, I hoped that some of you could point me in the right direction.

I know it could be A TON of different problems causing this code. But I will list the main problems I see on a daily basis, moreover I will write down the freeze frame stats from my OBD II reader and some live data.

Problems:

- rough idle on a cold start. Especially before the engine rpms drop, the car is shaking pretty bad. Not a rythm, but more like "random" vibrations. When the engine gets to operating temp, this is gone.

- I noticed a drop in perfomance after one of my ignition coils was changed. (But I could be playing myself mentally, don't be too quick to call this out...).

- Coolant leak (needs to be refilled once a month). No signs of any liquid and it seems to be more current during longer runs(getting to operating temp) and in the winter. This could maybe be a minor leak in the head gasket...? And could that trigger the code?

- Heavy/hesitant in first and second gear. This one is kinda funky, but it is best described as if the usual engine breaking is waay too effective...?? Gives me more the feel of a transmission or undercarriage problem.

Other than that it runs perfect.

OBD II Readings:

I am going to list all my info(probably a lot of bs you don't need, but I really don't know what's irrelevant...)

The Freeze Frame P0171(first numbers)                          Live data when warmed up, at idle(second numbers):

Fuel system 1 status:         CL                                              CL          

Fuel system 2 status:         N/A                                            N/A

Calculated Load value:        20%                                           9.4%

Engine coolant temp:         65C                                            91C

Short term fuel trim bank 1: Not available                              7.0%

Long term fuel trim bank 2:  Not available                              9.4%                  

Engine RPM:                      1082/min                                    759/min

Vehicle speed sensor:         0km/h                                        0km/h

Ignition timing advance for 1: -4                                           3

Intake air temp:                 13C                                           29C

MAF sensor:                      5.16g/s                                     1.72g/s

Absolute throttle position:  12.2%                                       10.6%

Shot term fuel trim(B1S1): Not available                               5.5%

Time since engine start:     412sec                                       376sec

Fuel rail pressure(gauge):  3890.0kPa                                  3900.0kPa

Commanded evapoative purge: 0.0%                                   0.8%

Barometric pressure:         102kPa                                      103kPa

Absolute load value:          30.7%                                       14.7%

Commanded equivalence ratio: 0.999                                   0.999

Relative throttle position:   2.0%                                         0.8%

Ambient air temp:             4C                                             10C

Absolute throttle position B: 12.2%                                    10.6%

Accelerator Pedal position D: 20.4%                                    14.9%

Commanded throttle actuator control: 2.7%                        0.4%

Phew...thank you if you took your time to read all that.

Be more than happy to leave a serious respond no matter how much or little experience you may have!