Surging?

[goldfinger]

Maybe you guys will have an answer for this.

The past couple days it has been warm enough to run the AC a little bit. I've noticed when I'm going down a particular hill at less than 20 the car seems to "surge". The tach dips from 1000, to 500RPM and you can hear the AC blower dip down with it. This happens whether I have the blower on 1 or 3 (haven't tried 2 or 4, but I'll assume it would happen on those also). It does not happen with the heater on or in the off position.

Now this doesn't happen on the highway or any other hill. Just one specific place coming out of a parking lot. It doesn't happen when I'm going down the hill, but rather at the bottom and when I start up the other side.

Any ideas? I know it's probably nothing to worry about. If I punched it I'm sure I wouldn't have the problem at all. But it makes me wonder.

 

[widman]

It's normal for an AC unit to put a load on the engine when the compressor kicks in, then the computer kicks up the RPM's to compensate if it is running below a certain treshold. Then some cars, more specifically smaller engines or those designed for gas economy, the A/C is designed to shut off the compressor during acceleration, so under certain conditions these two factors can colide to give the more than casual observer concern. My wife would never notice it if I had that type of sistem. For many people as long as the car starts, cools, and doesn't need to stop for gas frequently, they are happy.

 

[goldfinger]

quote:

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Originally posted by widman:
It's normal for an AC unit to put a load on the engine when the compressor kicks in, then the computer kicks up the RPM's to compensate if it is running below a certain treshold. Then some cars, more specifically smaller engines or those designed for gas economy, the A/C is designed to shut off the compressor during acceleration, so under certain conditions these two factors can colide to give the more than casual observer concern. My wife would never notice it if I had that type of sistem. For many people as long as the car starts, cools, and doesn't need to stop for gas frequently, they are happy.

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All good points. It is a 2.4L DOHC, so definatly a smaller engine. Too bad GM didn't make it economical.

As an update I tried this again today...... it ran absolutely perfect. I couldn't dpulicate the surging. Only thing I can think of different is I just filled up the gas tank. I could have had some bad gas on the previous tank.

Also, come to think of it I had just recently disconnected the battery to install a MP3 player so by doing that I reset the computer and it could have still been re-learning optimal air/fuel mixtures.

Who knows. It's fixed now, I won't question that.