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-Very- Rough Idle and engine dies + hot air

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  • 1 Post By Ray_Dockrey
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Old 07 Nov 2012, 01:45 pm
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Default -Very- Rough Idle and engine dies + hot air

Hi all, I have a 2006 non-turbo PT and she's been coughing a lot lately. Here are the symptoms:

At idle, with AC OFF, idle is normal.
At idle, with AC ON, idle is very rough and, sometimes, the engine dies.
At idle, with AC ON, there will be a loud click, the car will shake, and hot air will start coming out of the vent.

It also happens during reverse (if I'm reversing but not pressing the gas) and the AC is ON, it will cut off almost every time.

I first thought it was a fuel injector problem (I recently changed the spark plugs and the spark plug wires (thanks to help from PTCruiser links!) and I'm certain the plugs were properly gapped, so I'm guessing it's not that).

But I was told that it doesn't sound like an injection problem but that it could be one (or both) of these:

"This doesn't sound like fuel injectors at all. My first to suspects are the IAC (Idle Air Control) and the AC compressor.

Does the AC work fine otherwise? When not at idle. If so I am leaning more toward the IAC.

The computer on the car maintains idle speed by opening and closing a small air passage with a stepper motor. When you turn on the AC and put the car under more of a load the IAC should open up to compensate for the additional load. The passage may be clogged, or the motor may be bad.

I would remove the IAC and clean the passages, and the throttle plates with carburetor cleaner."


"We just had this fixed on a 2006 Cruiser. It was the cooling fan not running when needed on low speed. When stopped there was no airflow through the condenser, a/c pressure goes up, loading down the engine (slowing it and making it rough). In our case it was the fan, but we were told the fan controller often is the problem. We also had the warm air when stopped, which cooled off again when up to speed."

I'm guessing that it's impossible for me to replace the fan without a shop, so a mechanic will be doing that if it's the problem, but I'm also assuming that the IAC and the fan controller can be user-replaced. Is that correct?

What would be the best step-by-step process to diagnosing this?

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Old 07 Nov 2012, 02:12 pm
Ray_Dockrey's Avatar
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Join Date: May 2012
Location: Mustang, OK
Posts: 1,213
Default Re: -Very- Rough Idle and engine dies + hot air

What you describe is almost always the cooling fan. Here is how to replace it on the 01-05. I used to to replace the fan on my daughters 06. Its not too hard.

Removing the fan and housing 01-05 PT

Here is the testing procedure:

How to test my radiator fan?
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Last edited by Ray_Dockrey; 07 Nov 2012 at 02:17 pm.
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Old 07 Nov 2012, 03:28 pm
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Location: oak creek, wi
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Default Re: -Very- Rough Idle and engine dies + hot air

ray is absolutely correct.
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Old 07 Nov 2012, 03:52 pm
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Location: st james mo
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Default Re: -Very- Rough Idle and engine dies + hot air

cooling fan get a new one replace it and happy trails dont repace it and you will be doing a head job they are inder $100 at rock auto or ebay
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Old 08 Nov 2012, 06:41 pm
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Join Date: Mar 2011
Posts: 6
Default Re: -Very- Rough Idle and engine dies + hot air

Ok, that makes sense. One final observation: I sat in a parking lot today for about half an hour while wife was getting groceries and I left the PT on with the AC on as well. During that time the car did its normal shaking but over the course of the time I sat there, sometimes the AC would turn back on and get cold and stay cold for a while before it got hot again. And, the temperature never moved over half, which is where it always is - I thought the fan not turning would mean the engine would get warmer too?

Anyway, just wanted to post that bit of info also. But if it's still the fan, I'll pick one up tomorrow and get to work.
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Old 08 Nov 2012, 06:53 pm
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Location: Imperial beach
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Default Re: -Very- Rough Idle and engine dies + hot air

my pt does this as well.. if you dont really use the ac are you still in danger on having it blow the head from what ive read?
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Old 27 Feb 2015, 11:09 am
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Join Date: Feb 2015
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Default Re: -Very- Rough Idle and engine dies + hot air

i recently had some idle issues with my cruiser rpm's fluctuated at 1,000 rpm to 3,500 rpms i took advice from everyone in this forum and first cleaned the iac and throttle body with carb and choke cleaner.. never the less this lasted about a week before problems exsisted again.. i purchased the iac on line for 51.00 and installed in less than 5 min. .now my cruiser is back to normal .. thank you all for the replys and diagnoses.... happy motoring.....
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