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2001 Honda Civic EX

First noticed this problem when I got the car about a year ago. When the car is idling without the AC on, all is good. When I turn the AC and the clutch engages, it begins to vibrate, shaking the car with it. This used to be not so bad, but now that I've put about 15,000 more miles on it, it seems to be getting worse.

My guess is that the motor mounts are getting worn out. When I pop the hood with the AC on, you can see the engine visibly shake more than with the AC off. It's subtle, but noticeable. Anyone else have some advice on what the issue might be?

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The engine has no power at idle, it would be same as if you switch in gear and slowly release a clutch. Automatic idle control will try to keep it running, and it will vibrate. Some tiny 1L cars with AC needs to turn the AC off to get up the hill. It's a big load. If your idle revs are going lower with AC ON, then you can consider about checking the idle speed. Different cars have different idle speed, depends on a crankshaft and flywheel inertia.

To increase your idle speed you just need to open a bonnet and grab a flat head screwdriver. Warm up your engine, find a throttle body, and screw in this screw maybe 1/4 of a turn. See how it sounds then. You might need to screw it even less than 1/4. enter image description here

I stole a pic from another web site, supposed to be your car model throttle body and screw location.

You will notice your worn engine mounts if your car is shaking you forward and backward, making you bang your head to steering wheel and headrest, just because you're slow and almost not touching a throttle pedal. But rediculously vibrating engine is a too high load at too low RPM.

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  • Sounds simple enough. I'll give it a shot tonight. Thank you.
    – Jerreck
    Jul 18, 2016 at 17:23
  • I'd be wary of blindly increasing idle speed; just make sure it's in the factory specs, especially if the rough idle is a problem that didn't used to exist. If idle speed is at factory default and problem persists, look for the real cause.
    – Jason C
    Jul 18, 2016 at 17:24
  • Totally agree with Jason C, I hope your car have Tachometer so you can see what it does. Nothing will happen if it is a few hundreds higher, but it's bad if it is too low - can struggle with cooling system circulation (causing overheating), ignition timing (again overheating), oil pressure (LOL), charging, etc...
    – Arturs Bolsunovskis
    Jul 18, 2016 at 17:30

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