Is it normal for the LaCrosse tachometer to fluctuate up and down?
2 Answers
The fluctuation of the LaCrosse tachometer up and down is not normal, which is a manifestation of unstable idle speed. The reasons for unstable idle speed may include dirt accumulation in the throttle intake tract or carbon deposits around the throttle intake tract, preventing the control unit from accurately controlling the idle intake air volume. This results in an overly rich or lean air-fuel mixture, leading to abnormal combustion. The LaCrosse is a mid-size sedan under the Buick brand, featuring a 4-door, 5-seat sedan body structure with dimensions of 5026 mm in length, 1866 mm in width, and 1459 mm in height, and a wheelbase of 2905 mm. In terms of power, the LaCrosse is equipped with a 4-cylinder, 1.5T, 169-horsepower turbocharged engine, paired with a 9-speed automatic manual transmission. For suspension, the LaCrosse adopts a MacPherson independent suspension and a multi-link independent suspension.
That day when I was waiting at a red light in my LaCrosse, I noticed something wrong with the tachometer—the needle was dancing up and down like it was at a disco. This definitely isn’t normal. The tachometer should stay steady within a certain range; even when the A/C compressor kicks in, it should only fluctuate slightly. I suspect it might be due to dirty fuel injectors causing uneven fuel supply, or worn-out spark plugs leading to unstable ignition. If there’s a 'chugging' sound coming from the engine bay, chances are one of the cylinders has stopped working. The scariest possibility is an intake manifold leak—when rubber hoses age and crack, they suck in extra air, confusing the ECU. I’d advise against DIY fixes here. Last time I took it to the shop, they used a diagnostic scanner to pull the trouble codes and ended up replacing an oxygen sensor to fix it.
