Suggest to diagnose at workship, usually the keypoints of diagnose are:
1. Check the spark plug, fuel injector, catalytic converter.
2. Replace intake manifold; check/replace intake system exterior part.
3. Check the internal mechanism of the engine, including the wear and tear, maintenance and lubricating conditions.
4. Check if there is crack or damage on the exhaust manifold, is there damage or leakage on the silencer.
5. Check/replace timing belt, tensioner and idler pulley is suggest to replace at the same time.
6. Check the piston wear condition and if there is leakage at the valve; repair or replace the parts which has sever wear condition or leakage.
7. Check all vacuum tube if it is loosen, deteriorated, cracked or fell off.
8. Check if the lubricant still in good condition; perform engine check