my honda accord 2000 model with 4 plug engine vibrates if the a/c is on and the car is on drive while on hold say traffic or just idling.This doesnt happen if the a/c is not on.I also noticed that the tacometer reading fluctuates immediately I swith off the a/c but become steady if I trottle once or twice.The tacometer gradually rises from slightly below 1000rpm to slightly above about 1250rpm each time I start the car after the engine had cooled down but drops to 1000rpm immediately I switch on the a/c.The fuel consumption of the car is also on the high side.Apart from all these,the car works perfectly well.
What could possibly be resulting to the above problems?Thanks!

I am sure your CEL is ON with all these symptoms mentioned. Kindly get a place to scan your car to reveal the codes and tell the exact cause of these problems. From experience, it could be the idle control valve but my advice is that you get it scanned and avoid a guess work.

Best Regards.

Eastside Engineering Ltd