Volkswagen Sharan, 2012, Porvoo

The car vibrates when accelerating.

Mechanic's report:

(Auto electrician / Diagnostics): The car was examined at 1,700–2,400 rpm; the vibration is worst in 2nd gear. It was tested on a lift and everything at the front of the drivetrain was checked and found to be OK/secure. The gearbox adaptations were reset using a diagnostic tester. Injector values OK, rail pressures OK, air mass OK, EGR OK; the EGR was also temporarily blanked off, without helping. We have run out of ideas as to what could cause this vibration. It feels more pronounced on the passenger side, and I would like to replace the passenger-side driveshaft again in case there is an issue with the tripod joint in the replacement shaft. I cannot think of anything else. Mechanic's report (Transmission mechanic): Test drive and reading of measured values. Clutch pressures were read from the transmission side; under hard acceleration, clutch 2 pressure remains 1.5 bar lower than clutch 1 pressure. As all other drivetrain components except the mechatronics had been replaced, the mechatronics solenoids for clutches 1 and 2 and the main pressure solenoid were replaced with others (used parts from a corresponding working mechatronics unit from our stock), along with the oil, filling procedure and basic mechatronics adjustments.

-This had no effect on the vibration, although clutch pressures improved by approximately 1 bar during acceleration. The left driveshaft was investigated further; when the wheel was rotated, vertical runout could be seen on the inner-joint side. The driveshaft was removed and the inner joint dismantled; no clear fault was found, but replacing the left driveshaft with a new one should still be tried. No other clear cause of the vibration can really be found.

-Further measurements were taken with a diagnostic tester from the ABS sensors, etc.; everything appears to be OK. The vibration is less noticeable when cold and worsens as the vehicle warms up. Engine compression was checked and was even in all cylinders. The position of the engine mounts was corrected, with no effect. The timing-belt support rubber is not quite identical to the original, but this does not affect operation. The front brakes were checked on a brake tester; no distortion or other runout was detected on the gauges. The car was driven on a lift with the wheels off the ground; there was no runout in the tyres or wheels. Other drivetrain components, such as driveshafts and joints, cannot be properly checked while driving on a lift because the joints and other components are not in their normal driving position.