Just wondering if anyone can help. Engine surges while A/C is running- seems worse when outside temp. is hotter. You can see the tach going up and down about 300 rpm and can noticably feel it surging. Any help would be great thanks in advance. 97 Civic Lx no bells or whistles.

 

Your engine has to "surge" when you turn the A/C on. When you turn the A/C on, the engine must turn the belt for the A/C. This takes power away from the engine and will cause the RPM to drop. To counteract this, the computer makes the engine turn at a higher RPM so that when the compressor cycles on the RPM will not drop. The opposite will happen when the compressor cycles off. The compressor cycles on and off constantly because of the way the A/C system is designed.

 

The engine surges the entire time A/C is on, at an idle or acceling. I know the compressor will cycle causing a "surge" but not non-stop. A/C has a full charge so I now it isn't low or overcharged. It does seem worse the hotter it is outside. On 90 deg days it will almost stall at idle, idles fine w/o A/C.

 

It sounds like your problem is that your engine isn't "surging". Look at the Idle Air Control because this controls the amount of air that enters the engine at idle. When the A/C is one, does the RPM go up and down the entire time?

 

It doesn't always surge(9 out of 10 times it does) but it will do it constantly at idle or any speed. ( in town or hwy) Only when A/C is on. I wondered if it might not be the MAF sensor, I didn't even think about the IAC .

 

Your car doesn't have a MAF sensor, it does have a MAP sensor. What makes you think that the MAP sensor could be at fault?

 

i had the same problem, i brought the car to the mecanic and he redid the freeon. he said it had .8 of a pund too much freeon and the compressor would automaticall shut off when the pressure would get too high. the car would run like sh*t w/AC and run great W/o AC. i would check your freeon

 

another thing you can do is swap out that crappy 134a with some r416. it runs a few degrees cooler and and you get lower head pressure on a load. the r416 doesn't have to idle as high. it works good on my car.