I would be tempted to return it to the mechanic that originally replaced the timing chain and give them a chance to review their work as it may be possible something has not gone back correctly when reassembling.
The fact that the engine is running is a good sign that it is not timing chain related (we hope) but more anciliary items such as Air Conditioning pump or drivebelt that is too loose/tight, loose pipe(s)....worth checking the obvious stuff first which may be easy to resolve