The ac unit in my civic has been messed up 3 years now and I think its about time to fix it.First of all when I first turn it on it bogs the motor down pretty badly,but runs all right for about 5 minutes. Or so.Then once I get up to speed such as on the interstate at about 70 the compressor starts cutting on and off about every 3 to 5 seconds and its VERY noticeable like its lagging the motor down with it.At idle the compressor stays on but as soon as you rev it up the compressor shuts off but when it goes back to idle it cuts on and off repeatedly.It has plenty of freon and the pressure on the low side stays between 30 and 40.I have no testers for the high side though so I don't know what the pressure is on it.It still blows cold,but I'm too afraid to use it thinking it might blow up or something.Any answer would be apprieciated.Thanks

With the engine idling, and the A/C on, check the sight glass for any bubbles. If you see any, the freon is low. The symptoms you describe sound like the system is low on freon. Buy an inexpensive 134a manifold set on eBay and check both high and low pressures.

Well, awile back I thought it might be low to but the more freon I put in it the worse it got.

This is why you need a manifold set. It's necessary to watch the high and low pressure sides of the system, while filling with freon. Otherwise, too much freon can be added, where the compressor drowns in fluid. Yes, you are wise not to run the compressor, until some freon can be removed. Irreparable damage can result to the compressor, from overfilling the system.