“Engine Misfire and Jerking in Hyundai Santro on CNG—Is the CNG Filter Clogged?”

Home > Gari Forums > Hyundai Forums > Hyundai Santro Forums > Hyundai Santro Clogged Filters Forums

“Engine Misfire and Jerking in Hyundai Santro on CNG—Is the CNG Filter Clogged?”

My Santro starts jerking and misfiring when on CNG, especially when I accelerate. On petrol it runs better. A mechanic said the CNG filter may be clogged o r the CNG kit needs servicing. Before I spend money, I want to know if clogged CNG filters are a common issue in Pakistani Santros and how to diagnose it properly.

Talha Kyanii asked on 05 Dec 2025 10:14:12 am

1 Answer

11 views |

Gari Master - on 05 Dec 2025 10:16:05 am

On Santro, jerking on CNG is very common and often caused by a clogged CNG filter.

Common causes for CNG jerks:

Clogged CNG filter – Most common and very cheap to fix.
✔ Fix: Replace the low-pressure CNG filter and high-pressure one if needed.

CNG kit needing tuning – Mixture often becomes too lean.
✔ Fix: Proper CNG tuning with analyzer not manually.

Weak ignition coil o r plug wires – CNG requires stronger spark.
✔ Fix: Replace worn coil o r wires.

Dirty throttle body o r MAP sensor – Affects both fuel types but more noticeable on CNG.
✔ Fix: Clean throttle body + check MAP sensor vacuum pipe.

Valve clearance out of spec – Older Santros often need adjustment.
✔ Fix: Adjust tappets every 20,000 km.

Most common fix:

Changing the CNG filter + fresh CNG tuning solves jerking for most Santros in Pakistan.