What is the reason for the car not shaking when the oxygen sensor is unplugged but shaking when installed?

[DiSarah]

The reason for the car not shaking when the oxygen sensor is unplugged but shaking when installed is that the oxygen sensor is damaged. In this case, it is necessary to go to a 4S shop or auto repair shop to replace the oxygen sensor. The following is the relevant introduction: The impact of a damaged front oxygen sensor on the car: Excessive exhaust emissions; deterioration of engine conditions; the vehicle stalls at idle; inaccurate engine operation and reduced power; the engine computer cannot accurately judge the mixture condition; affects the normal operation of the three-way catalytic converter. The role of the oxygen sensor: The car oxygen sensor is a key feedback sensor in the electronically controlled fuel injection engine system. It is a key component to control car exhaust emissions, reduce car pollution to the environment, and improve the fuel combustion quality of the car engine. The oxygen sensor is installed on the engine exhaust pipe. Maintenance of the oxygen sensor: Check the working status of the oxygen sensor every 30,000 kilometers. If it is aging or failing, clean or replace the oxygen sensor in time.

[StJocelyn]

Seeing this question reminds me of my neighbor Old Zhang's old Excelle. We had the same issue last time. The engine actually ran smoother with the O2 sensor unplugged, but started shaking when plugged back in—most likely a sensor problem. It's responsible for telling the ECU the air-fuel mixture ratio. If the ceramic sensing element is cracked or the heater wire has poor contact, the data jumps around like an EKG, leaving the computer clueless on how to adjust the fuel injection—hence the shaking. Last time I hooked up a scanner to Old Zhang's car, the air-fuel ratio in the data stream was flashing wildly. Replacing the sensor fixed it right away. Oxidized wiring connectors can also cause this—sometimes they make accidental good contact when unplugged and replugged, but the problem returns later. Best to check the voltage with a multimeter to be sure.

[HazelLynn]

I've encountered this situation twice myself, especially common in vehicles over eight years old. Disconnecting the oxygen sensor forces the ECU into open-loop control mode, where it injects fuel based on default programming without referencing exhaust data, and surprisingly, the engine stops shaking. However, if the sensor is contaminated (e.g., by leaded gasoline or silicone sealant) when reconnected, its output voltage signal remains abnormally low. This causes the ECU to misinterpret the mixture as too lean and excessively increase fuel injection, resulting in an overly rich mixture that actually leads to unstable combustion. Once I removed a sensor turned white by coolant immersion - cleaning didn't help, only replacement solved it. As a reminder, aftermarket parts with poor signal accuracy can also cause shaking.

[OMax]

Engine shakes when O2 sensor is plugged in? Most likely a wiring issue. While the sensor itself could be faulty, it's more common for the wire harness insulation to be worn through. Last week I repaired a Bora with this exact problem: when unplugged, the exposed wire wasn't grounding, but when plugged back in, the connector shell pressed against the damaged insulation causing a short. The ECU compensates automatically when no signal is received, but goes haywire when it gets a short circuit signal. Using a multimeter showed normal heater circuit resistance, but zero resistance between signal wire and ground - tracing the wires revealed insulation worn through near the firewall penetration. These hidden faults are the hardest to diagnose - you need to disconnect the plug and test the harness condition.