AndrewDickerson

Hi All,

I am at my wits end with my vehicle and this p0171 code, I'm hoping there is a master diagnostician here who can help me as I no longer know where to look.

Model: 2007 c180 Kompressor
Vin: WDC2030462R261104
Engine Number: 27194630861788

The history:

1. About 3 months ago I started to get hight Long Term Fuel Trim Numbers, its started at a locked +16,4% and the Short Term Trims would subtract around -6% under load and shoot up to -16,4% when I released the gas and slowed down. At idle the short Term works itself down to 0% sometimes going to +2%.
2. The Fuel System Status goes to Closed Loop at Idle, once load is applied it moves Closed Loop Fault and when decelerating and no gas is applied it bounces to Open Loop Drive.
3. About a month ago it got worse, Long Term moved up to 18,5% and short terms bounced as above but more aggressively, this brought on the below work:

• Fuel System: New Fuel Pump and Sender Unit (Pierburg), New Fuel Pressure Regulator (Merc Original), New Injectors + Seals (Merc Original)
• Intake System: New Intake Manifold Seals (Merc Original), New Throttle Body (Bosch), New Throttle Body Seal (Merc Original), Supercharger Removed (All gaskets resealed with Locktite), Every Hose in the intake loop was then removed, cleaned, checked and refitted.
• Exhaust System: New o2 Sensors Fitted (Merc Original), flanges resealed and manifold checked by two specialists for leaks.
• Ignition System: New Spark plugs (Merc Original), New Ignition Coils (Beru OE)
• Sensors: Maf Sensor (VDO OE), MAP Sensor (Merc Original), Cam Positions Sensors x2 (Bosch OE), Altitude Sensor (Merc Original), Cam Magnets (Pierburg)
• Michelanious: Evap Solenoid changed (Merc Original), and PCV valve + the three rubber hoses under the supercharger changed. (Merc Original)

After all of this work the Long Term trim has gotten worse, it is now at +21.2% and the Fuel System still cycles CL, CL-Fault and OL-Drive as above. The Short Term still subtracts when under load, usually around -7%, more so when freewheeling to a stop and when standing still is can shoot up to +16%.

The o2 sensor reads between 0,300v and 1,200v but shoots up to around 4v when under load and accelerating.

I have propaned the engine bay a number of times now and cannot find an intake leak, what else could cause the above scenario?

I would love to save someone else this horrific experience, I will act on any good advice given and post detailed feedback, if we can find a solution I will post a nice break down of what went wrong.

All work above was completed by me personally, I can give feedback and explain if necessary. If any further live data is required please just let me know.

C230 Sport Coup

Forgive me for not reading every repair made, but I didn't see MAF
and that + leaking hoses is what solved my problem on my 02.

Tafa94

Hello AndrewDickerson ,i have same problem my stft cloes to 0 and idle but ltft +25 all all time its not moving , did you fix it? Thank you

Muhammed786

I I disconnected the egr and all the vacuum hoses. This is the aluminium pipe the runs alongside the power steering reservoir and bends down under the manifold. Super easy to do with the right tools. Cleaned out all the soot that was blocking especially where it enters the block. Not sure if it will make my P0171 message go away but I have also checked all you have done to yours. Try it guys let me know if it works for you.