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Hey y'all, I could use some help as I am having a frustrating issue with my 95 civic ex coupe: recently had thought that my surging idle woes were gone after I replaced my radiator thermostat and o2 sensor n did a whole flush/fill/bleed of the coolant. My CEL was giving me a primary o2 heater circuit code that went away immediately after that whole thing was done, and the idle surge went away for a while. It seemed to do it only when the car was cold at first, but had gotten worse before the maintenance above. This was just a couple months ago and I don't drive much - only a couple days a week sometimes.

Now the idle surge is back. It jogs between about 1000 and 1500 RPMs usually coming shortly after I start the car, but not immediately, maybe after I drive a half a block or so, and doesn't go away when it gets warmed up. It doesn't APPEAR to be a bubble in the coolant system since I've tried bleeding it several times now. Although I did notice that the coolant was low in the reservoir once after the radiator replacement, the level doesn't appear to have dropped again since then.

At one point after I had done the radiator/thermostat/o2 sensor change I got a single CEL that was either 22 or 21 (can't remember which - only that it was vtec related) but that went away on the next start and hasn't returned at all, so I thought it might be due to the weather we had, which was rather extreme cold or hot (can't remember which). But I am not getting any CEL now despite the surging idle problem.

Other than that, it appears to be running well - passed CA smog with flying colors. No power issues or anything, just the idle going wonky in Neutral at stops and such. (It's a manual 5 spd transmission)

Any ideas what could be the issue? What should I do next to troubleshoot?

I should mention I know f***all about cars. I'm a little 5'3 chick who is good at following instructions and handy enough to pull off some decent mechanical work as long as the instructions are good. So pictures and diagrams indicating what part is what when advising is especially appreciated, or at least what section to look it up in the service manuals (of which I have several).


It's bumming me out to have my victory over the last problem so short lived. But I guess it could be worse considering the car is 17 years old. I've had it since there were only 35 miles on her and literally drove it until the wheels (or rather ONE wheel) fell off of it, and I even have a youtube video of that part! ( ) Can't afford a new one just yet, so she is gonna have to go a little bit further , so thanks for any info or clues you can give me towards solving this.

 
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One thing you might want to check out is your IACV (Idle Air Control Valve) on your air intake. If that gets gunked up and doesn't work properly, that can cause your engine to have that idling issue. Next time you have the car running and the hood up, try closing back completely on the throttle valve, and if your engine starts to sputter out, then take it apart and spray some brake or carb cleaner on it, and see if that solves your issue.

 
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I had this same issue with my 98 EX Try what J-master said. here is what i did

Crank up the car, pop the hood pull off your intake and look inside above the IACV. there should be an open spot there, if so just cover it up with your fingers and see if the idle issue stops, if that is the problem you can just buy the new part, which for me was $312 or just bypass it by covering it with something.

I just cut a peace of hose and put it over the hole the vacume will pull the hose down snug then make sure u sucure it with something. i just epoxy it to the intake lol. $3 fix and seems to have knocked off my issue

 
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It may be that your fast idle valve is faulty or not getting coolant to it. I've seen a few older cars that clogged the steel coolant tubes that lead to the valve. This keeps the valve from warming and it leaks unwanted air into the intake. There are 2 coolant hoses attached to the valve, check them when the car starts to warm up and see if they are warm. Usually the tubes that clog are attached to the breather tube that goes to the back of the valve cover.

 
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I had the problem on my 94 after cleaning my IACV. I ended up having to replace it with one off of ebay. Worked fine after that. But I would try cleaning it first. It's attached to the back side of the throttle body.

 
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thank you all for the suggestions - I am going to start the troubleshooting and see what shakes out. I'll post back when I find out what the fix is