Civic's Idle Air Control Value problem, somone help?

Question

I have Honda Civic 98 EX. ever since i got the timing belt, and water pump changed, my "check engine" light turned on. and the computer says's it's Idle Air Control Value,
So i put in the new IAC and after about 40 miles the light came back on.
I showed the car to a mechanic. and he said same thing. so he put the used IAC in. and it worked fine for about 150 miles. and reset the computer and the light turned back on after 80 miles.. i don't understand what's causing it?
anyone know how to fix the problem, I'll appreciate it. b/c my inspection is expired, and I'm trying to get it fixed quick.

Troubleshooting P0505
Probable Causes
1. Vacuum leak on engine (checked that)
2. Dirty throttle body (not sure, how to?)
3. IAC motor defective (changed twice,didn't work)
4. Poor electrical connection to the IAC value (mechanic checked it, it's not that)

so what else could be worng?

Answer 1

The code P0505 is being set by something that is causing the idle to run either more than 200 RPM above the 'target' idle or more than 100 RPM below the 'target' idle for more than 20 seconds. If it happened after you changed the timing belt and never happened before that then something was altered during the timing belt replacement that affected the engine idle speed. The simplest answer is that the idle was set either too high or too low or the timing was advanced or retarded to change the engine idle from "before" to "after". It is also possible that the timing belt is one tooth off causing the idle to be too low or too high.

The problem was never the IAC valve. The mileage between when the light was shut off and it came back on (40 miles the first time; 150 miles the second time) is a function of the two-test cycle criteria for determining that a problem exists. There are specific test criterial that must be met for the system to detect a failure. The light is not illuminated until the failure is first detected and then a second failure is detected on a consecutive test cycle to confirm the first failure. The elapsed mileage is just an indication of how long it took to confirm the problem still existed, not an indication of how long the replacement part took to fail.

so, look to whatever was changed during the timing belt as the cause of your problem. Check the idle, the timing, the orientation of the timing belt and also the valve adjustment as probable causes.

Hope that helps

General Description
A target idle speed that meets the engine operating conditions (coolant temperature, A/C ON or OFF, etc.) is stored in the
engine control module (ECM)/powertrain control module (PCM). The ECM/PCM monitors and controls the idle speed so that
the actual idle speed is equal to the target idle speed. If the actual idle speed varies beyond a specified value from the target
speed (too low/high) over a certain period of time, the ECM/PCM detects a malfunction in the idle speed control system and
a DTC is stored.

Answer 2

Idle Control Valve Honda Civic

Answer 3

the top on the sensor is the only concern that strikes ! the sensor is the two screwed into the throttle physique or it has 2 screws ! take it off and clean the top ! it incredibly is a vacuum leak if the idle comes and is going ! in case you have a severe idle then it may desire to be the idle air administration or the butterfly up interior the throttle physique marvelous up and must be wiped clean !