Alright guys. Weather's getting colder in Northern WV and I want to have everything squared away for my car so I don't have to mess with this facet over winter. I've been trying to cure my idle problems since it started getting cold. In the summer, the car idles perfectly.

Car is a 95 Civic Ex Sedan. D16Z6
Mods: AEM SRI w/ dry flow filter. Poor fitting coupler to TB.
Skunk2 intake manifold. Stainless headerback exhaust, test pipe.

NO CELS

Now that it's gotten cold, my idle is TERRIBLE. Starting the car, it pegs 2K rpm and holds for 10+ seconds. After that, it has the surging idle with drops. 1.5k to 8k back and forth and it would ONLY go away once the car reached 190*F operating temp. Now, the idle is surging all the time and when it does even out, it's sitting at 1.1k warm idle. Something is not right.

Things I have done: Cleaned the IACV, and eventually swapped an IACV with an old one I had laying around and it didn't make a difference

I removed the FITV today and I noticed the seat for the plunger had backed out quite a bit so I put it all back together and screwed the seat all the way down and then backed it out half a turn.

I also adjusted the ignition timing on the car today at an attempt to make sure it was not advanced or retarded at all.

Please help me cure this! It's an annoyance and an embarrassment!

 

Get a can of carb cleaner and start spraying. You probably having a vacuum leak somewhere.

 

I should also mention that I have deleted the charcoal system on my car several months ago and also I have done an ABS delete and replaced with all hydraulics from an EG and using a 3030 prop valve.

I will actually go check for vacuum leaks right now. I have the port on the TB plugged where the charcoal canister line ran and the other large-diameter vacuum port plugged on the intake manifold plugged as well.

 

Doused the entire intake manifold with a can of carb cleaner while the car was warming up, and absolutely NO spikes in engine speed. Once it was warmed up, I gassed it just a little, and as soon as it drops back down it began surging again. Checking hoses by hand resulted with coolant on my hand so I'm going to track down the coolant leak in just a few.

 

I have the same problem on my civic. Didn't happen in the summer at all. as the weather got colder, the rpms would spike while the car warmed up. now the rpms spike when i don't give it gas. it doesnt idle correctly at all now the weather is below 65 degrees. i have plenty of coolant ( just replaced cooling system ) im going to take a video of my tach after I drop my kids off this morning. it's driving me crazy.
93 jhmeg8 d15b7 frankencivic ..

i've only had a honda dealership work on this besides myself, no rednecks!

found my wiring for my lights in some areas is just falling apart so at least i should have my half assed HID's working soon =/

 

I replaced the line that had the coolant leak and still no change. I'm noticing that the only way to get it to idle properly once it's warmed up is to give it some kind of electrical load. Turning headlights on or the blower fan on high makes it steady out.

Granted I lost a little bit of coolant when I swapped the hose out but i don't think it was any considerable amount.

 

If you lost coolant, you gained air. You need to bleed your coolant system.

 

I found this video to be very informative.

 

I'd like to think I'm pretty well versed in the coolant system on my car. I just can't seem to track this down. I burped the coolant system and wcontinued adding coolant after the thermostat opened. No change in idle at this point. Sitting steady at 1.1k rpm hot or cold. If I turn the blower and the headlights off the idle starts surging and dropping again.

I'll chek the video.

 

Think I may have found the problem. What is the small sensor onthe corner of the intake manifold opposite the throttle body? It mounts on the corner and has a small vacuum line running to it.

And what is the thread pitch of that screw that holds it in place.

 

Scratch that. That sensor is for the evap and it is no longer needed as I have deleted the charcoal system from my car. So I plugged the vacuum port on the back of the intake manifold and no change in the idle.

I'm thinking that I may have backed the fitv plunger seat too far out when I checked it out and that is the cause of the high idle.

Unplugging the iacv is the only way to get the car to idle properly and when I do it runs like ****. I will be switching back to my old IACV later on this afternoon.

 

UPDATE

Swapped the iacv's again to put the old one back in after cleaning it with brake parts cleaner and q-tips and letting it set to dry in the sun. Car now idles perfectly. About 1k at cold start and about 650 rpm when warmed up. No surging no jumping no fluctuation.