Hello all, my gf recently purchashed a 95 civic ex with 188,xxx miles 5spd all stock. And since then it's been having fluctuating idle issues. The car drives fine and warms up fine, but once warmed up at a stop light or something, the engine will fluctuate from 800-1500 rpm(but it idles around 1k rpm coasting down a long hill) . This also happens everytime right at start up when the car is warm, then maybe 30 sec - 1min. later, it will go to normal idle.

I've cleaned and adjusted the FITV. There is still a small suction on the bottom hole when warm, but I've plugged the hole w. my finger while the idle is fluctuating, but it didnt do anything.

I've bled the cooling system.

I've cleaned the IACV that came with the car and even tried 2 brand new ones, and the problem still occurs. The fluctuation dissappears when I unplug the IACV though.

Ive sprayed throttle body cleaner all over the intake mani, and vac hoses to check for vacuum leaks, but the idle didnt change at all.

Brand new O2 sensor, spark plugs and coolant temp sensor.

I saw a thread posted from sometime last week, and the OP thought it might've been the brake booster leaking. I disconnected the vacuum hose from the mani and plugged it, but it still does it at warm start up.

I've also disconnected the pcv hose, and plugged the vacuum source just to eliminate any vacuum leaks, but it still didnt fix the problem.

Could the MAP and TPS sensors cause this? I've been searching on how to check the sensors but each ones I come across give different wires to check. Can someone give me a link with the right answer? lol

I hope someone can help me out as im getting frustrated with this car

Thanks in advance

 

just a suggestion. put your hand over the throttle body while the car is running. If it dies you have no vaccum leaks. If it stays running find your leak.

 

Any CEL codes? Does the CEL work?

Is the throttle cable adjusted too tightly? There should be about 1/2" of free play.

Have you tried adjusting the idle speed?

 

sorry for the late response but the CEL is not on. And I've tried resetting the idle multiple times and still no luck. I tried another MAP sensor on there just to see but the problem is still there

 

sounds like a vacuum leak to me.

 

^This or an intake air leak.

OP, did you check the vacuum hoses to the cruise control, FPR, and EVAP system?

Might the TB or IM not be torqued to spec? Or have bad gaskets?

Are the rubber seals for the IACV or FITV leaking?

 

Im also leaning towards a vacuum leak but I just cant find it.

The rubber seals are all sealng. I've checked the FPR and EVAP hoses. I dont see any vac lines going to the cruise cntrol box (its the black box right by the driverside motor mount right?) I took it off but I didnt even see any vacuum port for it.

I'll be replacing the TB gasket tomorrow and see what happens.

 

spray carb cleaner on and around the throttle body when teh engine is running. if the rpm's spike then u know something is leaking

 

sorry haven't responded in a while. Ive done a bunch of other stuff since my last post but the problem still exist.

Changed both TB and intake mani. gaskets
Bypassed the FITV
And today I found a guy on CL parting out a complete manifold. SoI swapped the TB from that manifold but still no go. I also swapped the EACV and the purge solenoid just to see if it does anything.
I dont know where to go from here. All sensors/valves on the intake mani have been replaced. Ive checked for vac leaks multiple times.
Can something else beside a vac leak or faulty sensor cause this? Something with the ignition maybe? Im running out of ideas!!

 

GL man, having similar probs myself. I removed and cleaned the TB on my setup and it made it slightly better but still very obvious.

 

Did you try adjusting the idle speed exactly as described in the diagram?

Are you able to stop the idle fluctuation by fully or partially covering the IACV hole inside the throttle body?

 

Find a way to smoke out the intake manifold and see where the smoke comes out of...buy a smoke machine..or pull out a cig...inhale one...pull off a line...blow smoke in intake....put finger over hose..look around 4 leak