Dear,
Below is what i get from workshop manual of swift whose link i have given above, hope this will help and resolve your issue along with suggestions by h211186:
Poor fuel economy or engine performance
1.Possible cause1:Incorrect ignition timing Correction :Check related sensors and CKP sensor plate.
2.Possible cause2: Faulty spark plug(s) or high-tension cords Correction: Adjust, clean or replace.
3.Possible cause3: Faulty ignition coil assembly Correction: Replace.
4.Possible cause4Faulty CKP sensor or CKP sensor plateCorrection: Clean, tighten or replace.
5.Possible cause5Faulty CMP sensor or sensor rotor tooth of camshaft Correction: Clean, tighten or replace.
6.Possible cause6 Faulty knock sensor Correction: Replace.
7.Possible cause7 Faulty ECM Correction: Replace.