I have a 93 Civic that pusaltes at idle. I have checked for vacuum leaks and have not found any. I have found that when I disconnect a vaccum hose from that runs from the MAP sensor to the intake, the idle smooths out. After 30 seconds or so the check engine light comes on and the car stalls. Relace the vacuum line and the car starts up and begins its pulsating idle again but without stalling. I have installed a used MAP sensor as a replacement but it did not fix the problem. I know that the used part could still be the problem. Is there any way to check the sensor or is the fact that when the vacuum line is unplugged the car runs better for a short time an indication of the problem? Or could it be something else, and what pray tell could that be?

 

I have the exact same problem as this and i just failed inspection for it too . Someon help us out. BTW i have a 95 cx w/ CAI and 2 1/4 catback. Stock motor.

 

any ideas on what to do for this problem. I tried cleaning my iacv but that didnt work. Does my car have a fitv to adjust by any chance and where would it be located? PLEASE HELP.

 

Any excess air that enters the motor can cause this idle surge. Vacuum leaks, IACV, FITV, EGR not seating when closed, bad PCV, throttle cable too tight, and idle screw out too far can all cause a high idle. When the idle exceeds ~1200 RPM with the engine warm and the throttle plate is closed, the ECU cuts off the fuel injectors. The idle falls below the threshhold, the injectors cut back on and the whole cycle starts over again. I had a starting boost valve(accord) that was leaking through the diapham that caused mine. Something like that can only be found with a vacuum pump/guage. Anything that has a vacuum line running to it can cause this problem if it won't hold vacuum, not just the vacuum lines and gaskets. This includes EGR diaphram, Boost valve diaphram, cruise control, MAP, Intake bypass valves, Purge solinoids and others depending on model.