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98 Civic hatch - fluctuating idle when A/C is on

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Old 07-31-2011, 10:18 AM
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Default 98 Civic hatch - fluctuating idle when A/C is on

Originally Posted by 2kul
sorry haven't responded in a while. Ive done a bunch of other stuff since my last post but the problem still exist.

Changed both TB and intake mani. gaskets
Bypassed the FITV
And today I found a guy on CL parting out a complete manifold. SoI swapped the TB from that manifold but still no go. I also swapped the EACV and the purge solenoid just to see if it does anything.
I dont know where to go from here. All sensors/valves on the intake mani have been replaced. Ive checked for vac leaks multiple times.
Can something else beside a vac leak or faulty sensor cause this? Something with the ignition maybe? Im running out of ideas!!
I'm in the same situation as you and it's also driving me insane. I'm bout to sell my car and the hell with it.
Old 08-02-2011, 06:06 PM
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Default Re: another fluctuating idle thread - 95 civic ex

The thing is that for me it only happens when I have the A/C on. When the A/C is off, it doesn't give me that issue.
Old 08-02-2011, 06:15 PM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by civichb98
The thing is that for me it only happens when I have the A/C on. When the A/C is off, it doesn't give me that issue.
Have you recently done any work on the A/C system? Does the A/C have any problems? When the A/C is on, does the condenser fan run?
Old 08-04-2011, 05:41 AM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by RonJ@HT
Have you recently done any work on the A/C system? Does the A/C have any problems? When the A/C is on, does the condenser fan run?
I have not done any type of A/C work to it, it's still the orginal from when the car was new. The condenser fan does go on but the only thing is that the compressor is making a funny noise from what I'm thinking it's coming from. Cause when the a/c is on, the car sounds and idles weird, and when the a/c is off, the car sounds normal and idles fine. If it is the compressor, why would it cause this problem???

I had forgot to say that I have a '98 Civic Cx Hatchback with these issue.
Old 08-04-2011, 05:46 AM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by civichb98
I have not done any type of A/C work to it, it's still the orginal from when the car was new. The condenser fan does go on but the only thing is that the compressor is making a funny noise from what I'm thinking it's coming from. Cause when the a/c is on, the car sounds and idles weird, and when the a/c is off, the car sounds normal and idles fine. If it is the compressor, why would it cause this problem???

I had forgot to say that I have a '98 Civic Cx Hatchback with these issue.
Also check whether the condenser is heavily clogged with bugs/road debris or the fins are bent and occluding air passage through the condenser. If that's fine, either take the car to a reputable A/C shop or hook up a manifold gauge set and read the low and high side pressures with the engine idling at 1500 rpm. Post the readings.
Old 08-04-2011, 10:01 AM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by RonJ@HT
Also check whether the condenser is heavily clogged with bugs/road debris or the fins are bent and occluding air passage through the condenser. If that's fine, either take the car to a reputable A/C shop or hook up a manifold gauge set and read the low and high side pressures with the engine idling at 1500 rpm. Post the readings.

Ok, I'll see when I can find someone to do that for me. I'll let you know as soon as I get it checked out, thanks.
Old 08-11-2011, 05:58 PM
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Default Re: another fluctuating idle thread - 95 civic ex

Yo RonJ@HT, I want you to take a look at my vid's if you can please., but I don't know how to upload them on here.
Old 08-11-2011, 06:02 PM
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Default Re: another fluctuating idle thread - 95 civic ex

Upload the video at YouTube, and then post the link in your thread.
Old 08-12-2011, 06:21 PM
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Default Re: another fluctuating idle thread - 95 civic ex

A/C Pressure Test On 1,500 RPM
http://www.youtube.com/watch?v=S-o4T...ature=youtu.be

A/C Pressure Test On Idle
http://www.youtube.com/watch?v=Y2Mpn...ature=youtu.be

Let me know what you think

Last edited by Former User; 08-12-2011 at 09:42 PM.
Old 08-12-2011, 08:03 PM
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Default Re: another fluctuating idle thread - 95 civic ex

You've got some issues. a 134a system should NOT be running anywhere near 275 psi on the high side unless it's about 140 degrees where you are. You're probably tripping off on high pressure. This would explain the weird noises from your compressor. It's working wayyy too hard.

Before you go evacuating and recharging your system, make sure your condenser fan is running, your condenser itself is as clean as you can get it and your evaporator is clear of leaves, dirt, bugs, etc. If either one of these is dirty, you'll get crappy readings on your gauges.

Looking at your videos again though, high discharge pressures, low suction usually points to a restriction in your expansion valve.
Old 08-12-2011, 09:35 PM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by Frozen E
You've got some issues. a 134a system should NOT be running anywhere near 275 psi on the high side unless it's about 140 degrees where you are. You're probably tripping off on high pressure. This would explain the weird noises from your compressor. It's working wayyy too hard.

Before you go evacuating and recharging your system, make sure your condenser fan is running, your condenser itself is as clean as you can get it and your evaporator is clear of leaves, dirt, bugs, etc. If either one of these is dirty, you'll get crappy readings on your gauges.

Looking at your videos again though, high discharge pressures, low suction usually points to a restriction in your expansion valve.
The condenser fan works, the only thing is that from the middle of the condenser down the fins are pretty flat. Tomorrow I'm going to use a condenser comb to fix the fins and then degrease the condenser.
Old 08-12-2011, 09:39 PM
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Default Re: another fluctuating idle thread - 95 civic ex

Fin combs are pretty much useless on automotive condensers. They work so-so on your home one. Different fin setups.
Old 08-12-2011, 09:40 PM
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Default Re: another fluctuating idle thread - 95 civic ex

I got one from my job that has 4 different sizes
Old 08-12-2011, 09:40 PM
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Default Re: another fluctuating idle thread - 95 civic ex

So then I'm going to have to change my condenser????
Old 08-12-2011, 09:46 PM
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Default Re: another fluctuating idle thread - 95 civic ex

What was the temperature outside when you did the pressure tests?
Old 08-12-2011, 09:48 PM
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Default Re: another fluctuating idle thread - 95 civic ex

In the 80's, it was tested in the morning.
Old 08-12-2011, 09:54 PM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by civichb98
In the 80's, it was tested in the morning.
Low or high 80s? High humidity like Houston? Is the A/C blowing cold?
Old 08-12-2011, 09:59 PM
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Default Re: another fluctuating idle thread - 95 civic ex

It's in the mid's 80's in the morning, plus I was in the shades. Yea, the air is blowing cold.
Old 08-12-2011, 10:13 PM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by civichb98
It's in the mid's 80's in the morning, plus I was in the shades. Yea, the air is blowing cold.
Based on a chart in the service manual, your low side ~18 and high side ~270 are both on the low side. I would have expected pressures more like 40 low/350 high.

Describe your idle problem. Does the compressor clutch seem to cycle on and off constantly with the A/C running, causing the idle speed to jump around? Any CEL codes?
Old 08-12-2011, 10:26 PM
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Default Re: another fluctuating idle thread - 95 civic ex

Ron, where are you seeing that a 350 psi high side is a good thing?

That's insanely high for a residential R22 system, and even more insane for one charged with 134a.
Old 08-12-2011, 10:46 PM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by Frozen E
Ron, where are you seeing that a 350 psi high side is a good thing?

That's insanely high for a residential R22 system, and even more insane for one charged with 134a.
Using the service manual pressure/temp chart, I assumed 85F and high humidity. The two horizontal lines are the approximate expected low (red) and high (green) side pressures -- it looks like ~41 psi and ~340 psi. The chart states that pressures should be read at 1500 engine rpms.



The pressure switch doesn't open until the high side pressure reaches 455 psi or above.

Last edited by Former User; 08-13-2011 at 06:41 AM.
Old 08-13-2011, 07:20 AM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by RonJ@HT
Based on a chart in the service manual, your low side ~18 and high side ~270 are both on the low side. I would have expected pressures more like 40 low/350 high.

Describe your idle problem. Does the compressor clutch seem to cycle on and off constantly with the A/C running, causing the idle speed to jump around? Any CEL codes?
The compressor does cycle on and off, and I don't have any CEL.
Old 08-13-2011, 07:30 AM
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Default Re: another fluctuating idle thread - 95 civic ex

So Ron, your saying the my pressure is fine?
Old 08-13-2011, 07:30 AM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by civichb98
The compressor does cycle on and off, and I don't have any CEL.
It's normal for the compressor clutch to cycle on and off, but not if it does so very rapidly, for example every 5 seconds. When you did your pressure test at idle, I did not notice much cycling so I'll assume that this is not a problem. This together with the fact that your A/C is blowing cold, I don't think that your A/C system is the root cause of your idle problem. So let's refocus on your idle problem. Please again describe it in detail.

Originally Posted by civichb98
So Ron, your saying the my pressure is fine?
Based on the chart, your refrigerant pressures are a bit low, but since your A/C is blowing cold, I would leave it alone for now.
Old 08-13-2011, 07:43 AM
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Default Re: another fluctuating idle thread - 95 civic ex

Originally Posted by RonJ@HT
It's normal for the compressor clutch to cycle on and off, but not if it does so very rapidly, for example every 5 seconds. When you did your pressure test at idle, I did not notice much cycling so I'll assume that this is not a problem. This together with the fact that your A/C is blowing cold, I don't think that your A/C system is the root cause of your idle problem. So let's refocus on your idle problem. Please again describe it in detail.



Based on the chart, your refrigerant pressures are a bit low, but since your A/C is blowing cold, I would leave it alone for now.
The cycle doesn't come on every 5 seconds. It still kicks on normal.

Ok, when the a/c is on and only the a/c while I'm driving and coming to a stop or red light. When I let go of the clutch and the RPM is dropping back down to it's position it's suppose to be, it slugs for a quick second and go's back to it's regular idle. I would like to record it but I don't have video on my iPhone since it's the 2nd gen iPhone that I have. I can explain it more over the phone if you'll like.


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