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Engine Shakes When a/c ON

 
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  #1 (permalink)  
Old 01 Apr 2018, 04:23 pm
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Location: miami, florida, USA.
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Default Engine Shakes When a/c ON

When a/c is off no shake.
I think this happened once before but can find it in my notes or searches.
Think this forum told me to change some sensor in the a/c system, that would make the engine rev up a little for the added a/c load.
-Two speed fan working, new spark plugs, cable and ignition coil, all recently.
thanks
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Old 01 Apr 2018, 05:30 pm
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Default Re: Engine Shakes When a/c ON

With the engine cold, start the engine, turn on the A/C and see if you hear the radiator fan come on almost immediately. If you don't hear it come on please don't drive the Pt Cruiser until you find out why the radiator fan does not come on. Manually apply 12 volts to the radiator fan to see if the fan might be faulty. If the Pt Cruiser still has the original radiator fan it might be due for replacement.

If both speeds are good on the radiator fan I would suggest you check your lower and upper motor mounts (torque struts). Does the engine have alot of movement when you shift it from reverse to drive?
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Old 02 Apr 2018, 06:29 pm
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Default Re: Engine Shakes When a/c ON

Fan checks out as you explained, the torque struts are good also. I have previously replaced both fan and struts.
Upon playing closer attention to this noticeable vibration, it occurs when:
1-Engine well warmed up
2-Stopped at a red light, for instance
3-It doesn't always happen, but is noticeable in my well taken care of car and an engine that works perfectly, well almost.
4-I think I hear a noise at same time it vibrates, almost sure it's on the front driver side.
Well, I guess I may just have to wait until it gets worse so it's more identifiable. Do you agree?
Thank you so much for your reply.
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Old 02 Apr 2018, 06:55 pm
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Default Re: Engine Shakes When a/c ON

Quote:
Originally Posted by rcalzadilla View Post
Fan checks out as you explained, the torque struts are good also. I have previously replaced both fan and struts.
Upon playing closer attention to this noticeable vibration, it occurs when:
1-Engine well warmed up
2-Stopped at a red light, for instance
3-It doesn't always happen, but is noticeable in my well taken care of car and an engine that works perfectly, well almost.
4-I think I hear a noise at same time it vibrates, almost sure it's on the front driver side.
Well, I guess I may just have to wait until it gets worse so it's more identifiable. Do you agree?
Thank you so much for your reply.
I would suggest check the other mount on the drivers side if the vibration and noise is coming from that side.

Does this Pt Cruiser have automatic or stick shift? Does it vibrate more if you rev the engine in neutral or park?
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Last edited by ptcruisersteve; 02 Apr 2018 at 07:09 pm.
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Old 02 Apr 2018, 06:58 pm
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Default Re: Engine Shakes When a/c ON

It's automatic.
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Old 02 Apr 2018, 07:00 pm
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Default Re: Engine Shakes When a/c ON

I am sorry, noise comes from passenger side!
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Old 02 Apr 2018, 08:40 pm
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Default Re: Engine Shakes When a/c ON

I would suggest checking to see if the noise is coming from the A/C compressor when you turn on the A/C. How is the freon level?
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Old 04 Apr 2018, 09:24 am
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Default Re: Engine Shakes When a/c ON

The vibration turns off when a/c is turned off, for sure.
Don't have the gauge to check freon level but the a/c is very cold as it has been for the last 14 years (without any repairs to the a/c system). I am in Miami, FL.

Maybe the engine is not increasing enough rpms when a/c on?
Is there a sensor that regulates this and maybe it's failing or false contact?

I appreciate your interest very much.

PS: Checked my cylinders compression at 104,000 miles Feb 2017, and got the following: #1-182PSI #2-184 #3-184 #4-182. Thought it might be interesting.
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Last edited by rcalzadilla; 04 Apr 2018 at 01:27 pm.
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Old 04 Apr 2018, 10:31 am
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Default Re: Engine Shakes When a/c ON

If you had replaced the torque struts (upper and lower motor mounts) yourself did you do the factory alignment and if so what was the final measurement?
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Old 04 Apr 2018, 11:07 am
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Default Re: Engine Shakes When a/c ON

Quote:
Originally Posted by rcalzadilla View Post
The vibration turns off when a/c is turned off, for sure.
Don't have the gauge to check freon level but the a/c is very cold as it has been or the last 14 years (without any repairs to the a/c system). I am in Miami, FL.

Maybe the engine is not increasing enough rpms when a/c on?
Is there a sensor that regulates this and maybe it's failing or false contact?

I appreciate your interest very much.

PS: Checked my cylinders compression at 104,000 miles Feb 2017, and got the following: #1-182PSI #2-184m #3-184 #4-182. Thought i my be interesting.

You have a 2001 so when you turn on your A/C, the PCM triggers the IAC (Idle Air Control) valve to increase the idle speed to compensate for the load then being applied by the A/C.

If your PT was mine I would either clean and adjust the IAC or replace it. Replacing it would be my first choice. You will find it attached to the throttle body.

If that doesn't fix it, then I would look to the compressor being faulty and dragging the idle rpms down to far.


Jerry

Last edited by wwpptc; 04 Apr 2018 at 11:42 am.
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