There is nothing to be offense.
Why cylinder missfire? Because of below reasons.
fuel and air mixture
Weak or Loss of Spark
Loss of compression
fuel and air mixture-
1. when there is not enough petrol in the mixture to burn.A dirty injector / bad fuel pump will not let enough petrol to flow in the cylinder and a missfire in that cylinder will occur.
- Petrol is enough but Air is not enough or more than required - then again there will be no or weak ignition in cylinder and result will be a missfire. Leaked air filter box will not let enough air to burn injected amount of petrol. Why we always say to check the air filter box? because in case of leaked filter box, engine will not get all the air sucked through TB.
Weak or Loss of Spark -
If due to any reason, spark is not proper at tip of plug then there would be a missfire in that cylinder.It could be due to worn / damaged / cracked spark plug, Bad coil, cracked distributor cap.
Loss of compression
If not enough compression, most of the air fuel mixture loss before it get ignite and result will be missfire. Possible reasons are bad exhaust valve or blown head gasket.
Missfire on CNG
On CNG cylinder dont get any fuel through Injectors. Both the fuel (CNG) and Air goes through TB and if not properly tuned, there are more chances that one or more cylinder dont get enough amount of CNG+AIR to ignite.
Why u don't or rarely face missfire issue on petrol, because when on petrol each cylinder is getting fuel through dedicated fuel injectors.
Also u knw petrol can ignite with less spark+air in cylinder.