Contour Enthusiasts Group Archives Forums General Troubleshooting Intermittent power surge when A/C engaged

I left work yesterday and was in the parking garage. I turned the car on, let it run for about 20-30 seconds, and put the A/C in the "on" (not "max") position to run it for a few minutes.

Immediately, the idle began what I would call a "surge and settle" cycle. The RPM's would bump up to around 1,750 for about 1 second, then slowly settle back down to the "normal" 900 or so. The idle would rest at about 900 RPM's for 4 or 5 seconds, then bump up to 1,750 again and the whole cycle would repeat.

Once I left the parking garage, and was out driving, I could feel that intermittent surge even while the car was in gear - it was most pronounced when I was coasting in 2nd gear towards a red light - I could feel the car surge forward as the "bump" occurred. 4 or 5 seconds later, I would feel a surge again.

As soon as I turned the A/C off, the problem disappeared.

Anyone have any thoughts? Many thanks in advance for your ideas.

sounds normal. the compressor places a load on the engine, and as it cycles on and off, the load is thus removed/replaced.

Edit:

the "low" setting of your ac allows for shorter cycles of the ac, thus less cooling power, but shorter intervals of the "surges" you described.

This is normal and occurs when the AC or defrost is on.

I hate it. Good thing I dont have to use my defroster much.

It's normal for the A/C to to load the engine down, but it should not cycle that short unless it's fairly cold out. You are probably low on freon.

The idle should not change that much. Either the IAC is not responding well, or your idle mixture is near the limit.

If you have had no CEL's, you could try cleaning the IAC, MAF, and fuel injectors. Make sure the secondaries are closed at idle. Make sure the PCV is good and there are no disconnected or leaking hoses on the intake system.

Quote:

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The RPM's would bump up to around 1,750 for about 1 second, then slowly settle back down to the "normal" 900 or so. The idle would rest at about 900 RPM's for 4 or 5 seconds, then bump up to 1,750 again and the whole cycle would repeat.

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That kind of surge is definitely not normal. I had a similar problem over the winter with the defrost, which also runs the a/c compressor. Dealer replaced the IAC, and problem seemed to go away, it came back one nite for some reason and then went away again. I try not to use the a/c, or def. at all, but if i get it with the A/C this summer I have heard from numerous people that the A/C needs to be recharged so that's my next step, even tho the IAC helped tremendously, so I would try those two things.

1. Recharge A/C
2. IAC

Lemme know how it works out.