My 2006 PT Cruiser Turbo idles very rough when the a/c compressor is on. If I turn the compressor off the shaking reduces considerably but not totally. I had the plugs and plug wires changes, injectors cleaned and motor mounts changed. Problem still exists. Any ideas? Could the a fan motor fault cause this?
PT Cruiser shakes at idle
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1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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Welcome to Allpar. Proper motor mount adjustment is important. Verify that no metal-to-metal contact is transmitting engine vibration into the body when the A/C is engaged.
Another possibility is that the compressor is dragging and adding excessive load to the engine at idle. This can be from an over-oiled/over-charged A/C system or a failing compressor.
You ask about a fan motor fault, is there one present? Without a fan motor cooling the condenser, the high side refrigerant pressure will skyrocket at a stop and load the compressor, which will in turn, load the engine making for a slower, rougher idle.
Another possibility is that the compressor is dragging and adding excessive load to the engine at idle. This can be from an over-oiled/over-charged A/C system or a failing compressor.
You ask about a fan motor fault, is there one present? Without a fan motor cooling the condenser, the high side refrigerant pressure will skyrocket at a stop and load the compressor, which will in turn, load the engine making for a slower, rougher idle.
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Agree. The AC is a tremendous draw on the the little engine, to which the computer is actually designed to increase the engine rpm to maintain that draw to offset the draw. Everything has to be proper to work correctly.
Is this something that has just started after some tinkering with the AC, or has it always been this way?
Is this something that has just started after some tinkering with the AC, or has it always been this way?
I mentioned the cooling fan because someone on another forum said that a fault in the motor could cause it to draw excessive amp. I do not know when the problem started I just bought the car and thought it just needed a tune up. Apparently that was not the case. I do notice that the rpms at idle do not increase when turn the a/c compressor on. Also when I return to park the shaking goes almost completely away, even with the a/c on.
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That might have been me - happened to my 92 Daytona. It was the fan harness that had an intermittent short, and I wired a new, separate harness in because I could not find where the short was. The voltmeter would instantaneously dive to about 10V for a second or two, then snap back to normal. But I don't believe that's the issue here. Either the compressor is failing, or the motor mounts are not installed correctly. They are directional, it's important to install them in the same orientation as the original.
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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23,655 Posts
The engine idle should react to added load (within reason) by means of the PCM-controlled IAC (idle air control) motor. It tries to compensate changes in load to keep a somewhat stable idle speed.
The throttle body blade and bore can accumulate carbon deposits which can restrict air passage between them and the IAC (idle air control) motor can compensate somewhat for this.
A good scrubbing with a toothbrush soaked with throttle body or similar solvent and rinsing the carbon down the throat may improve air passage and idle quality. It is an inexpensive place to start anyways.
The throttle body blade and bore can accumulate carbon deposits which can restrict air passage between them and the IAC (idle air control) motor can compensate somewhat for this.
A good scrubbing with a toothbrush soaked with throttle body or similar solvent and rinsing the carbon down the throat may improve air passage and idle quality. It is an inexpensive place to start anyways.
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