Honda Car Forum

When i start my civic dx(1.3) in the morning, it is reving at around 4000-5000 rpm, however after 2-3 minutes, it goes down to about 800-1000rpm, regardless if the engine is hot or cold. is this normal? the manual says the idle speed should be at 800rpm. my car doesnt have a tach but i can surley tell it is not idling at 800. any thoughts on this?

It my be that it is the automatic choke which will come into operation as soon as the temp cools from normal.

Check your O2 sensors. If one is burnt out your engine with idle high trying to compensate for the emmitions. Any Auto Zone will test them for free.

It's a tuning problem. When the car's warm, all the fluids a flowing the way they were meant to. When it's cold if the oil is too thick for example you're gonna have high revs till it warms up enough to flow properly. The best fix is to make sure your injectors are clean and that your spark plugs have been serviced. Then check your oil weight to make sure you're running the optimum oil for the colder weather. Last but not least you could adjust your idle manually under the hood, but i recommend that as the last resort. Good Luck.

Check your sensors- your O2 may be at the end of its life.Also check for error codes, could be something wrong with another sensorCheck your air filter also

On some cars this is normal as your car may have an automatic choke, this means when you first start your car it revs a little higher than normal until the engine warms slightly. You may find if you press your accelerator once it has started the revs will go to normal, 750 - 800 rpm.

I had a high idle after travelling at speed & engine cutting out on cold mornings and found it was my idle control valve. I was told this can cause these idle problems. I removed mine from inlet manifold, squirted carb. cleaner through the holes in it & let it soak, min. of 4 hr.s recommended, & bolt to inlet manifold again. I now have no idle problems, handy when your cousin is a mechanic. Only thing is the valve is in a very inaccessible position, u remove & put back by feel only. Best of luck.

It also happens to my Civic. Check the sensors.

the first thing to try is bleeding the coolant incase of any air locks, just release the coolant nipple near the top pipe from the radiator until coolant starts coming out. if that don't help then take the air intake pipe off the throttle body, you will see 2 holes inside the throttle body, if the bottom hole is sucking in air block it and the idle should drop (maybe stall if the idle screw has been adjusted beforehand), if it does then its the idle control vavle (waxstat) under the throttle body (it has coolant ppes attached) remove the pipes and unblot it (2 bolts ones hidden on the far side of it) take it apart and screw the large white screw-type0thing inside it back in (over time they slowly unwind), put it together and reattach as before. (this is what i had to do when my crx was idling at 3-4k from cold and 1.5-2.5 when warm)if the bottom hole is not sucking block both holes, if the car nearly/or goes to stal then its another valve on the back of the intake manifold which will probably need replacing.