Hello everyone, I was very glad to see this topic because it relates to my problem somewhat.
I recently bought a Honda Civic VTi 2000 A/T. I noticed the same thing with my Civic, that when accelerated in neuteral gear the revs go up to 5000 and then the cut off sets in. This seems normal to me as there is a cut off in Efi cars, my car has CNG though and as rightly pointed out by many members here, there is no such cut off on CNG. Also, I'm pretty sure that the cut off on petrol too is if the car is idle, in neuteral gear, while driving I'm sure you can take it beyond 5000 revs without a bother.
I'm having a bit of a problem and I need some help from you all. The problem seems to be with my car's auto-race setting or possibly the ECU. When I start the car in the morning, revs stay up for a little while, i think around 1200 which i believe is the setting on the Auto choke of the ECU. After only a short while, this normalizes and the revs come to the normal level around 1000. Normally When I shift to an idle gear (N or P) The revs increase a little to about 1100 and they drop when I shift into a driving gear and I wanted to ask, is this normal. The thing that seems to me like a problem is though, that when i switch the AC on, the revs drop to almost 300 and the car starts shaking a bit. This is all with my car running on CNG. On Petrol also, a problem that sometimes occurs is, the revs keep increasing from 1000 to 1500 and then come back to 1000 as if the car is 'breathing'. Now i don't understand why this problem is happening. My mechanic mentioned something to me about a map sensor, is it the same as ECU ? Also a friend of mine said that there are 3 settings on the ECU i.e. the normal race, the auto choke and the cruising RPM. does this have something to do with that? Or does it have something to do with throttle body or throttle sensor?
Can you please tell me how to figure out this problem and fix it?
After I bought the car, I got some work done on it since it had done 80000 kms, I got periodic maintenance work done like timing belt change, transmission fluid change, radiator service, engine oil change and suspension work. Also there was a heating up issue with the car and I had to get some work done for its valve seals but now that issue is completely resolved and there is no such problem.
Please help me out here, if you want any other details I'd be happy to tell you