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I have a 2000 Chrysler Neon which generally runs well.

I have noticed that if I start the vehicle, turn the AC on and reverse out of the driveway, the engine seems to struggle/sounds like it is going to stall.

If I turn the AC off, it immediately regains power and runs fine.

If the AC is off the whole time, there is no struggling/stalling behaviour.

This also happens in a forward gear, but not to the same degree.

Once the vehicle is running, I can turn the AC to full without this symptom, but it still feels a little less responsive.

To give me an idea of where to start, what sorts of problems could cause these symptoms?

Could it be an issue with the battery, since presumably it would be at its weakest immediately after starting?

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2 Answers 2

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Air Conditioners are run by a belt that is connected to the crankshaft. The engine turning causes the A/C Compressor to move.

When your A/C is not turned on, a clutch disengages the A/C Compressor's internals from the pulley on the belt. This allows that belt to free spin, not adding load onto the engine.

When the A/C is turned on, that clutch is engaged and so the internals of the A/C Compressor are driven, this does add load to the engine.

If this is a new symptom, then it is a sign that the compressor is adding more load to the engine then it used to and could be signs of a failing compressor, the pulley starting to seize, need for lubrication, etc.

If it has always been this way and you are just curious as to why, it is simply additional strain being put on your engine by the A/C.

The fact that it has more of an impact at first start then once moving is not surprising. Your engine is not warmed up yet and not at its optimal running condition yet.

A/C systems impact the performance of all engines, however the smaller and less powerful the engine, the more impact is going to be noticed as the A/C systems are not proportional to the engine, they are proportional to the interior cabin space.

Take a vehicle that has a 4 cylinder and 6 cylinder engine option, the A/C unit is going to be the same as there is the same interior space to cool. However, you are going to notice the power impact far less on the V6 as it will be a smaller % reduction of power.

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A special note on the warmup. When in warmup mode the ECU may be running in open loop instead of closed, which means that it will go to the ECU mapped fuel mixture (which is normally extra rich for safety) and low timing advance values. Both of which reduce available power. As the oxygen sensor starts cycling reliably, you'll get closed loop fuel mixture, and as the coolant temperature comes up, you'll start to get more timing advance. –  Brian Knoblauch Jul 28 '11 at 12:22
    
It may also have a malfunctioning idle-up solenoid for when the A/C is on. –  Nick Nov 25 '12 at 1:39
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As a follow up for future googlers, my air filter was in a fairly bad state. This resulted in some power loss during normal operation but when I put additional load on the engine it really became noticeable.

Cleaning the air filter has made a world of difference.

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