LIANA CNG PROBLEM

AOA iam facing a problem on my liana, its idle RPM continously fluctuates between 400-600, and the funny thing is that its idle RPM is more with out AC, and less with AC, meaning to say with out AC 700-800 and with AC 400-600, now the problem is that due to such low RPM check engine light blinks and car shuts down some time, when i restart it it get started on petrol perfectly, its performance on petrol is perfect, but CNG performance is deterioted, due to this drop in RPM, its initial acceleration also get affected adversely, it is worth noting to mention that during driving i feel jurk of extra thrust as suddenly power increases but this happens just for few seconds, the problem related to RPM get more prnounced with AC and lights ON. i have taked my car to suzuki dealers, first they have adjusted gas it gets fine but after some time problem came again, i took it again then they adjusted tappet, cleaned the injectors and gas kit excluding cylinder, and changed the plug wire, it worked for a while but problem has risen again, then they advised to change the AC kuppi, which i have no idea what heck it is ?,,,,,, they said it maintain idle RPM when ever AC put on , personnely i feel i has something to do with IAC valve, although i my self cleaned all the sensors including mass air flow sensor, but it makes not much difference, few suggestions in my mind are


1. get IAC valve checked


2. get back to suzuki dealer for CNG tuning


i need advice from liana users and experts


lookin forward