low idling

[webby]

Ok take it easy on me here this is my first honda ever so I know little about them. With a/c off the car idles at about 700 rpms like it should and shifts a little high (4 to 5000rpms) on normal (half or so throttle) acceleration. However, when I turn the a/c on the idle drops to about 400 rpms. So low the car trys to turn off. Then it goes to about 6000 rpms before shifting and will not grab 4th gear. So at about 60mph I'm screaming along at 4000rpms. Any ideas what could cause this? I bought the car with a blow head gasket and a over heating in traffic problem. So I just put a rebuilt head on with a head gasket kit. Then I did a major tune up. The car had the same problems before I did all that.

 

[Joe Mason]

Sounds like your automatic transmission needs to be serviced or replaced. I would try servicing it first. New AT fluid and filled to the correct level can make a huge difference. The low idle could be caused by many different things. Do you have a check engine light (CEL) on?

 

[daperez13]

Hondas, specifically older Civics are so susceptible to accessories, even your blinker can cause your RPM's to fluctuate a tiny bit. What you're experiencing is a bit odd, though. Probably a good idea to replace the transmission fluid like Joe said, if it hasn't been done at the recommended service interval. Hook up a timing gun and check your timing with the A/C off, then with the A/C on and see how is it affecting it. Inspect the belt and check it's tension, adjust it if necessary. Does the A/C perform like it's supposed to?

I don't think the overheating issue has any direct affect to the low idling problem but it could have caused something else to disrupt it. Unfortunately, electrical is not one of my strongest suit but trying a different ECU might be worth a shot. Also, the A/C may be shorting out an O2 sensor or another component directly affecting your idle. Check your grounds and follow the wiring from the A/C as far back as you can to confirm they're not frayed or damaged otherwise.

 

[denisstranjina203]

check and make sure that the ac compressor isn't seizing up when engaging so that its not putting a bigger hold on the engine itself