Suzuki cultus misfiring on cold start

[awan.zarar9]

After allot of hassle and expenditure, I have finally decided to ask the real experts.

I have a 2010 Suzuki Cultus EFI (CNG variant)

I am fed up of this issue with my car.
It misfires on cold start, as soon as I start my car, initially the RPM rises as standard, after a couple of seconds, it begins to stutter/misfire.
If I hold the throttle at half it would misfire and not increase the RPM significantly.
If I drive the car, it would hesitate allot on low RPM, it will only be able to drive if I press full throttle.

However as the car warms up, the misfire would reduce. When temperature reaches half, if I restart my car, the missing is almost gone.

Now the car is totally normal when it warmed up, the misfiring is still there but unnoticeable.

Now you might immediately say that check the coil wires etc but let me tell you what I have done already.

New coil wires
Cleaned injectors
Cleaned spark plugs
Cleaned throttle body
New fuel pump (china/local)
Cleaned fuel filter
Adjusted tappets
New distributor cap (Kabli)
New distributor rotor
Replaced Fuel pressure regulator
Replaced Coolant temperature sensor
Disconnected CNG setup (eliminated cable connections)
Tested ECU parameters (&No codes except disconnected O2 sensor, not needed)

Someone please help me get out of this daily trauma and by the way, gasket is ok.

[pwuser150520264261]

Same problem in my baleno, I also checked almost everything you mentioned but yeah very annoying problem.....does your car drive fine or misfires while driving also? and what about idle, does it stall at idle or just stutter?

[aminaseo29]

Hey bro, I totally get how frustrating this can be, especially after trying so many things.
Since the issue mostly happens on cold start and gets better when the engine warms up, it could be something like the IAC valve or MAP sensor. These parts handle idle and fuel-air mix during startup.
Also, even though you said the O2 sensor is disconnected, sometimes it still affects cold starts. Might be worth reconnecting just to test.
Local fuel pumps can also struggle at cold start. If you can borrow one from a working Cultus, that might help rule it out.
Lastly, check for a vacuum leak cold engines can make small leaks worse. Look around the brake booster and hoses.
Hope you figure it out soon, man. Keep us posted if anything works could help others too.