hey everyone, recently the idle on my daily driver started to surge and i cant pin point where it is. so i need some suggestions please. its a 91 civic with d15 converted to mpfi.

problem: cold start idle normal, once at operating temp idle surges between 900-2100 rpm.
slight lost of power.

what i've tired: Replaced Pcv, sparkplugs, resealed throttle body,cleaned idle air control motor, checked tps made sure its .5v

 

Have you checked for vacuum leaks?

 

I had the same problem (on my D15) when I had my A/C fixed and recently when i put my motor back in. The car would idle fine upon startup - second you bump the gas it would start to surge. Both times it turned out that the throttle cable needed to be adjusted. Try loosening up the cable a bit.

 

make sure you have no air in your coolant lines, also try to clean your screen on the "iacv" idle air control valve, and as stated make sure no vacuum leaks

 

Help me understand. How will this make a cars idle surge? :-)

 

idle air control valve has coolant running in it, if there is air in the coolant lines the iacv will not get a proper reading and can cause the car to surge at idle

i just noticed you did clean iacv i would try to burp you coolant system

 

idle control screw too high?

 

no air in coolant. and yes i have cleaned the idle air as i said in my post. and for vac leaks no hoses look cracked,and i mentioned i even resealed my throttle body. idle screw has never been touched and i've checked it,good, throttle cable not too tight. even checked my dashpot its ok too :s

 

so you ever figure out what the problem is? my car is doing the same thing right now...

 

another update.. surging has stopped i did what a youtube video said about loosening nut on throttle body. i did it about 4 times before it actually fixed the problem. like i said it took me a total of four adjustments it probable came out to half a turn 180 degrees. after this i had to adjust my throttle cable because it made car idle to high. after 180 degree turn and throttle adjustment its no longer surging idle/ ghost idle....
pior to fix , i have done:
*replace iacv (idle air control valve)
*burp cooling system
*checked all vacuum hoses for leaks
*cleaned iacv
im sure im forgetting something but before doing any of this i would try this NUT 1ST, although cleaning the iacv screen is also a good idea as youe messing with all this. hope this helps someone .
HERES THE LINK:

 

lol oops i was trying to update my own post

 

My throttle cable is completely loose and it's idle is at 1500. Ideas?

 

most likely - vacuum leak somewhere

 

I have replaced every vacuum line. I have sprayed everything with carb cleaner while idling. I have taken a propane tag and ran propane around every possible vacuum area. I'm not sure what else there is

 

Hi,
l have a Civic 1.6l 2004 Hatchback with 272k Petrol+LPG.
While driving in city 20-30km/h the rpm drop and tent to stall, sometimes it stalls. I try pushing the throttle during that moment but it doesn’t go higher than 2000 rpm. The same problem happens when l drive in petrol or LPG. Fuel pump is ok. Battery ok. Sparks ok. Oil and filters ok. I’ve noticed that once the engine is at the right operating temp. it works fine even on idle. So l experience rpm drop after l turn on the cold engine to lets say 20-25 min of driving.
Any suggestion is welcomed.