I bought brand new Shimano ST-EF29 (3x8 Speed) Shifter + Brake Lever (both left and right) for my MTB which I installed some 3 months ago. But it is very noisy (especially when shifting from 3rd to 2nd chainring on the left shifter).
It changes super smooth and beautifully quiet from 1st to 2nd speed (chainring), a litle bit harder from 2nd to 3rd speed (chainring) but still satisfactory. The chain is not touching the front derailleur cage at 1x1 Speed and also not touching it at 3x8 speed).
But the noise is quite loud and annoying when shifting backwards from 3rd to 2nd and then from 2nd to 1st speed (chainring).
I noticed a small screw with the spring on the bottom side of the shifter and checked Shimano Tech website. It is called Reach Adjusting Screw and Spring (see photo). But it seems this screw is for brake lever adjustment so I didn't touch it at all.
Is there a way to fix this? Is there a screw on the shifter/brake lever that needs to be adjusted? The cable tension seems right when changing from 1st to 2nd speed but when changing from 2nd speed to 3rd speed it is a bit hard. The thing is that when shifter is in 1st speed (smallest chainring) the cable is completely loose) so I am not sure if loosening a cable tension (at front derailleur) furthermore would cause shifting problems.
The right shifter (Speeds 1x8) is working perfectly.
I have no clue how to solve this. At first I thought it's because the shifter is new so it will become better/quieter with the time but it is 3 months already and the noise is the same.