Greetings to all Members n Experts!!!!
I own a Cultus Euro-II November 2012 model driven 86,000 Km/s on Petrol (CNG never installed/used). Car is properly tuned after every 10,000 KM/s, spark plugs are replaced on every tuning, Air Filter is also kept cleaned to attain optimum mileage. All other things are properly maintained and giving excellent feedback. During recent tuning, my mechanic also serviced the throttle body completely. It gives my excellent mileage on petrol. Using Caltex Havoline Formula 10 W30 engine oil and is replaced every 3000-3500 Km/s.
The problem which i am facing these days is linked with the AC. During extreme temperature and with AC turned on, the car runs good but as i lift my foot from the accelerator without pressing the clutch, car starts knocking or you can say (Gives Jhatkay), not all the time but most of the time. The problem is more severe in 2nd or 3rd gear and in low speeds, while car remains completely smooth without AC. Recently i parked the car and left for shopping with AC turned on for 8-10 minutes. When i returned and was ready to leave, car was not picking up RPM with missing problem. After 3-4 throttle's the problem seemed to get minimized a bit. But after getting on road, the problem was gone.
Meanwhile i noticed smoke pipe was getting little black (Usually it remains brownish, throws water during winters, never gave smoke except very little smoke on initial startup during winters).
One more thing that i have noticed is that the problem is more severe when the AC is running on 3rd speed (Inner Blower Fan Speed), while it gives less problem when the AC is running on 1st or 2nd speed.
Looking for experts advice....