Engine noise at low revs under strain
I have a 2005 Murano with 85,000 miles on the clock. Been running beautifully but recently I have noticed a "rattling or knocking" noise coming from the engine. It is not very loud, and only happens briefly when putting the engine under strain - like pulling away at a traffic light when the car is on a slope. The more gas I give it, the louder the noise.
Also, it only happens when the engine is warm, not when it is cold and it only happens at low revs.
I thought it might be a "pinging" (or pinking) problem that one would get on the older engines when the timing was out, but I didn't think modern engines would do that.
Can anyone suggest where to start looking before taking it to a dealer and spending a fortune.