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The reason given to you was ridiculous, no carbon on the valves after 70k odd kms is a joke and that too that the work fine when there is deposit on them....:uncontrol....maybe he wanted to say something else and did'nt put it too well.

I would suggest get a diagnostic ecu scan done, atleast you will get to know for sure if the O2 sensor is malfuntioning for sure or there is some other problem. This would be the best you can do before going ahead with what any mechanic can say.
Mis-firing happens mostly due to clogged injectors, poor fuel quality, wrong or mis-matched AFR, electrical problems but you have already mentioned that the above have been checked and since re-setting the ECU gets rid of the problem for a while then there is a possibility of a sensor not working properly.

Do make sure that if GM advises you to change the sensor then insist on cleaning the sensor of carbon deposit and refitting the sensor and test it your self if the car responds normally, if not then go ahead with a change.

Incase you want to double check on scanning, the is a workshop by Delphi called Kar Scanners at Chirag Dilli(on the entry towards GK-II)
Phone Number-01129219915.

Do keep us updated

I am presumming you mean that the ECU detects clogged injectors due to which the AFR or fuel air mixture runs lean and thus mis-firing right?

Because the way you wrote it, seemed as if the ECU is a living creature which "FEELS":D

....Dont mind just pulling your leg....

hahaha i don't mind the jokes man. Cheers cheers:

Na, i'm not talking about the backfire, I was talking of the malfunctioning of the oxygen sensor.

Backfire is due to the more gaps in the spark plugs i guess. Because the same problem happens to my accent too whenever i changes the spark plugs.

Because the scanning had been done on the petrol not on CNG.
ECU behaves different on Petrol and CNG. Many components don't work when the car is on CNG.

Best Example is RPM Limiter. When ECU detects no Fuel, then limited went off. lol clap:

Even i was laughing like anything after hearing the explanation from my drive but ... :Frustrati

I am not sure this will happen, as stated everything remain normal once ECU is resetted and goes fine uptill a day or two. But problem starts arising after 2 days only.


Scanning was done on petrol as well as CNG, but still the problem arose !!

Just a wild guess Ashish but might help, if the problem is on petrol too then this does not apply.
With the temperature dipping in Delhi, CNG being a gas will become denser due to which a little adjustment of the AFR is required. Slightly more CNG inflow by adjusting the RPM controller valve on the kit or the power valve.

Also get the IAC valve checked but that should also mean fluctuating RPMs and idling.

I believe its definately gotta be electronic which is why after resetting the ECU its fine for a couple of days.

Any specific time of the day that the mis-firing occurs?

Even i am also very much sure that something electrically is culprit. Car seems to be starting very smoothing (i.e. half ignition only) today morning, as i had resetted ECU yesterday evening. :Frustrati

It might not be a CNG or Petrol Problem as if in case it had been everything hadn't gone fine with ECU reset.

i just got my baleno converted to cng. it has done about 45k kms. previously it was running on lpg. on lpg it was running very nicely. there was no noticeable difference as compared to petrol. now in cng i feel lack of pickup upto 1500 rpm. after that its running nicely. also when it gets converted from petrol to cng for a few seconds rpm would drop to around 400-500 and it wont respond. my kit is tomasetto with lambda and TAP. what is the problem? is it with TAP or lambda? i told the fitter to tune it twice but its still not upto satisfaction. by the way i also own a wagon r which runs very nicely on cng and it has only TAP.

it is because of the TAP which kicks in after 1500 rpm.

-No doubt LPG is a better fuel then CNG due to better combustion. However, still good points of CNG over LPG are quite endless like cheaper fuel and no foul smell etc. Though once tuned properly you'll be happy to have CNG which will be lighter on pocket and run nice as well.

-TAP kicks in after 1500 RPM that's why you feel a bit sluggishness while driving i'll suggest to look out for your driving style to get a better CNG experience.

-When the Fuel is changed to CNG, for a millisecond engine has practically no fuel in the fuel line which result in no response till 400-500 RPMs. Better practise is to get the kit tuned for CNG shifting RPM @ 2500-3000 RPMs.


Cheers

I got the timing advanced. Now the car responds nicely but the other problem i.e. no response immediately after conversion still persists. I went to another guy and he has promised to solve that too. Lets hope. I would also like to know which type of lamba is better, manual or automatic? I have automatic type with the present cng kit while I had manual type in the previous lpg kit.

Very very true, infact i still wonder why people convert to LPG kits whn lpg is not widely available, infact in all the places in delhi, i only know of two places where one can fill up LPG. Ofcourse there will always be people who use household cylinders illegally, but for production cars like Wagon R DUO etc, i really dont see the point. Cost of running on LPG at times goes over the cost of running on Diesel as fuel prices are at similar levels.

Not necessarily. The TAP will kick in any range of RPMs between 1000-3000, depending upon the level to which timimg has been altered/retarded and the state of tune of the vehicle.
Usually a TAP has 3 setting modes, 1st and 2nd stage is mostly used and recommended. At 3rd stage the car will go bezirk and the level of retarded timing poses a threat to the engine...which might lead to a blow up.

Spot on Ashish! But that lag for 2-3 seconds will always persist due to the fuel changeover, irrespective of the RPM at which swithover takes place.

Hi, Can someone please tell me what TAP Is, What it does etc?

please also realize, gujarat CNG is more like 26-30 bucks rather mostly diesel - dont know current rate :D

haha welcome abhik, phamilyman and ashthedivx after a long time.

in delhi its around 20 Rs.

I had instaled Lamda sensor, but car is getting detuned again and again, the CNG guy told me that its my Green Filter which is creating problem. Something wrong with the Filter or the lamda? I think i need to fit the stock airfilter and get it checked again.