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The engine vibrates abnormally after accident repair of GAC Toyota Camry.

2026-05-28

Background

Vehicle Model: GAC Toyota Camry

Fault Phenomenon

This Camry was involved in a traffic accident out of town two months ago, sustaining severe front-end damage. For various reasons, the owner did not have it repaired at an official Toyota 4S dealership and instead took it to a local independent repair shop nearby. Upon collecting the vehicle, the owner noticed abnormal performance: the car shakes severely at idle, as well as during takeoff and stopping. The repair shop claimed the shaking would subside after a period of driving since the engine had just undergone major overhaul.
The vehicle has been driven for more than a month with no improvement in the shaking issue. Recently, a new abnormal noise appeared when turning the steering wheel left or right. The car was sent to a friend’s repair shop for four days of troubleshooting, yet no root cause was identified. The owner now requests our dealership to diagnose and resolve all faults.

Fault Analysis

Technicians verified the symptoms on-site, matching exactly the customer’s description: violent engine vibration, and a distinct "click" noise emanating from the chassis when turning the steering wheel left or right at low speeds.
After opening the engine hood, technicians discovered numerous improperly fitted engine components; the engine had been fully disassembled during prior repairs, and most replacement parts installed were non-OEM components. The technician discussed conducting a comprehensive vehicle inspection with the customer, who agreed and left the vehicle at our shop for further diagnosis.
First, the technician reinstalled all misassembled engine parts and retightened every chassis bolt. It was found that the through bolts on both left and right lower control arms were not fully torqued down. After properly tightening these bolts, the steering click noise was completely eliminated.
As for the persistent engine shake, the technician outlined potential root causes as follows:
  1. Resonance between the vehicle body and engine
  2. Malfunctioning ignition coils
  3. Defective spark plugs
  4. Faulty fuel injectors or associated wiring harness
  5. Intake system malfunction
  6. Exhaust system malfunction
  7. Internal mechanical faults within the engine


Repair Plan & Troubleshooting Process

Routine preliminary inspections were carried out:
  1. All three engine mounting cushions were inspected and found in good condition.
  2. Cylinder cutout testing was performed on ignition coils, and spark plugs were removed for visual inspection; no abnormalities detected.
  3. Cylinder cutout testing for fuel injectors returned normal results.
IT-2 diagnostic scanner retrieved no Diagnostic Trouble Codes (DTCs). Live data streams were then captured, including readings from the oxygen sensor, mass air flow (MAF) sensor, fuel injection pulse width, and engine RPM. When compared against data from an identical undamaged Camry, the faulty vehicle displayed abnormally low oxygen sensor and MAF readings, with engine RPM fluctuating erratically between 735 and 983 r/min.
Using oxygen sensor data as the primary diagnostic reference and applying reverse troubleshooting logic: the oxygen sensor voltage only fluctuated within 0.01–0.03V. Based on the sensor’s function and operating principles, this reading confirmed the air-fuel mixture was consistently too lean (excess air, insufficient fuel), indicating an air leak in the intake system.
Focused inspection of the intake piping and vacuum hoses downstream of the MAF sensor revealed a cracked, aged vacuum hose connecting the PCV valve to the intake manifold, damaged by prolonged high operating temperatures.
The technician temporarily sealed the cracked hose, which greatly reduced engine vibration and stabilized RPM at 739 r/min. However, subtle abnormal shaking remained when benchmarked against other matching vehicles. Further inspection uncovered a failed canister purge solenoid valve that had been modified to remain permanently open.
After replacing the damaged PCV hose and faulty canister purge solenoid valve, followed by throttle body cleaning, all vehicle performance returned to normal.


Summary

Improper repairs performed by a non-Toyota authorized shop created multiple man-made faults, complicating secondary diagnosis. By methodically analyzing symptoms, applying professional technical knowledge, cross-referencing live data with a reference vehicle, the technician successfully located and rectified all defects, significantly improving customer satisfaction.