Hi Gurus, My 4JX1 engine is vibrating on idle. Idle speed is about 750rpm. At hgher speed the engine runs smooth. The problem is the engine dies off in the middle of driving. Sometimes it will start again and sometimes the vehicle has to be towed. What the the main problem and how can I adjust the idle speed up.

Are you running the recommended oil grade? As the injection system is operated by engine oil pressure using the wrong oil grade can prevent your car from starting, running smooth or hard starting! Ideally they require a 5W30 oil grade. Idle speed is controlled by the engine control unit! It's a common rail diesel engine so there's nothing to adjust! The Camshaft position sensor could also possibly be intermittently faulting causing similar symptoms! It's located on the front of the cambelt cover(gray coloured sensor)