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I have a 97 civic ex and when im idling in both park and drive its not smooth but not terrible however I live in texas and worship my A/C, so its on most of the time, thats when the idle is like a jackhammer.
I've checked my motor mounts and theyre nice and tight, I just had a cat and new a new header put on if that helps any but it did it prior to that, just not as bad.

Any help would be great!!!

 
Rep Power: 228

Hook up a scan tool to check whether the engine is idling to spec with and without the A/C load. Any CEL codes? When was the last basic ignition system tune up?

Did you check the two front torque engine mounts? They tend to fail by the age of your car. Did the rubber on the side mount crack, allowing the fluid to leak out?

Have you tried cleaning the IACV?

 
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No CEL triggers or anything, I'll hook up my scan tool tonight after I get out of class.
My Last Ignition system tune up was about 2 months ago, I havent checked the torque mount and im not leaking any fluids so i dont think the side mount is cracked however I'll double check that. MY IACV is fairly new maybe about 6 months old if that? Thanks for the speedy reply!
I'll go over everything you listed

 
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First thing, the idle will never be stable with the AC running. I would check the idle in park and drive with all accessories off, if it seems good then do not worry about. Idle problems can be numberous things, anywhere from a tune up to a bad computer.

You said header, was it an aftermarket header? You might want to try a idle re learn as well.

 
Rep Power: 228

Not really true. The ECU tells the engine to increase the idle speed when the A/C is on to compensate for the higher load. I have two 6th Gen Civics that do not shake badly when the A/C is on.

 
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Idle re-learn meaning disconnect the battery for 10 minutes and then reconnect, let the car idle with nothing on?

 
Rep Power: 228

The ECU can be reset by removing the 7.5A hood Back Up fuse for a few minutes. Did the rough idle start after the cat/header replacement?

 
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Sorry in class so I'm posting from my phone, its always been a little rough but more so after the replacements.
Could it maybe be a faulty O2 sensor? Both of them are fairly new as well, replaced them when I replaced my IACV

 
Rep Power: 228

No, I don't think so. Focus on the other items I mentioned.

 
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will do, I'm thinking I just may ditch class that way I still have a little daylight left.

 
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Let me clarify, I meant with the on and off of the compressor the idle will move up and down, I know from experience, even when I turn on the rear defroster or other access. IMHO the best gauge of the idle quality is with all accessories off. My EX never had a perfect idle even from new, I think it is trait of the sohc engine. The idle is decent but never perfect, I am sure other owners can agree.

Another thought he can try adjust the idle with the set screw but must follow the honda adjustment guidelines in the manual.

 
Rep Power: 228

I never would characterize the normal Civic idle as "jack hammer".

This may be worth trying after more basic problems are ruled out.