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1999 BMW Z3 Roadster 2.5L Excessive Emissions, Poor Fuel Economy
Posted to European Driveability on 3/9/2026 7 Replies

Negative -28 STFT, both banks. All 4 oxygen sensors are reading full rich at about .93v ECT reads around 200-205 fahrenheit when warm. Vehicle is in closed loop. The crazy part is if the hose connected to the valve cover is disconnected, the fuel trims go ...

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car Vehicle Data

1999 BMW Z3 Roadster

VIN 4USCH9338X
Engine2.5 L / 6 cyl / GAS
Trans5-speed Standard
DeliveryFuel Injection / Fuel Injected
EmissionsOBD-II Compliant
SymptomsExcessive Emissions, Poor Fuel Economy
OccursAlways

Trouble Codes

P0172Fuel System Too Rich (Bank 1)
P0175Fuel System Too Lean (Bank 2)
Open Help Request

car Vehicle Data

1999 BMW Z3 Roadster

VIN 4USCH9338X
Engine2.5 L / 6 cyl / GAS
Trans5-speed Standard
DeliveryFuel Injection / Fuel Injected
EmissionsOBD-II Compliant
SymptomsExcessive Emissions, Poor Fuel Economy
OccursAlways

Trouble Codes

P0172Fuel System Too Rich (Bank 1)
P0175Fuel System Too Lean (Bank 2)