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My 1998 civic has an idle problem, it goes up and down when warm and has a p0505 iac code and when Itry to keep my speed steady it kicks.Should I change my iac?, my map sensor?or my entire intake(used)?thx
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Usually this is a vacuum leak. It also could be low on coolant, so the IAC (idle air control) valve isn't getting coolant to warm it up. The IAC valve itself could be the cause.
Error Code:P0505 Fault Location:
Idle Speed Control (ISC) System - Malfunction Possible Cause:
-Wiring harness.
-Idle speed control (ISC) actuator/Idle air control valve (IAC) valve.
-Throttle valve tight/sticking.
-Engine control module (ECM).
The IAC is on the bottom of the throttle body and has a hole in the bottom of the throttle body that lets air into the IAC. YOu do not have to remove it, if you do remove it the throttle body would have to come off and a new gasket would be required. Usually spraying through with throttle body cleaner will clean the IAC so it functions properly. About your P0505 faut code, The IAC (Idle Air Control) valve controls the idle speed of the engine. At idle the throttle plate is closed, of course. The IAC is computer controlled and allows only a certain amount of air around the throttle plate. This metered air controls the idle speed. The IAC has a "plunger" or "shutter" that moves to open or close the bypass air passageway. The more air the IAC allows around the throttle plate, the higher the idle. The PCM (Powertrain Control Module) uses the IAC valve to keep the idle speed correct with varying engine demands. Can be a three or four wire sensor depending on the model. The PCM monitors voltages of the IAC circuits and if it detects an incorrect voltage on one or more of the IAC motor circuits it will set P0505. NOTE: Problems with the IAC would only be noticeable at idle or when throttle is closed. Symptoms may include:MIL (Malfunction Indicator Lamp) illuminationEngine stalls and may not idle unless throttle is depressedIntermittently stalls when letting off the throttleEngine may idle too high Potential causes of an P0505 code include:IAC motor connector is damaged (check connector and pins for damage, and moisture)One or more IAC circuits open or shorted to groundOne or more IAC circuits are shorted to voltageIAC has failedPCM has failed Possible Solutions:This should be a fairly straightforward diagnosis. Start by clearing the fault codes. Then unplug the IAC and start the engine (This may cause other IAC codes to set. Just ignore them for now). If the P0505 code doesn't reset, replace the IAC. It is internally shorting one of the IAC circuits. If the code DOES return after unplugging the IAC and starting the engine, then you know it isn't the IAC motor. Visually check the wiring harness all the way back to the PCM. You may need to visually inspect the harness by removing all the insulation off the wires. It is possible that the wires could be shorting to eachother or to other wires in the harness. If there are no wiring problems, and the code keeps returning with the IAC unplugged, you can check the PCM by removing the IAC wires from the PCM connector (or clipping the wires in a location where they can be repaired easily) and then start the engine (If you're not sure, don't do it. Take it to a qualified professional). Now if the code doesn't reset there is a problem with the wiring. Check for continuity on all the IAC wires. Any resistance points to a problem. Check for voltage on any(At this point there shouldn't be any voltages on the wires because they're clipped at one end and unplugged at the IAC). Repair as necessary. But if the P0505 code DOES reset after removing the IAC wires from the PCM connector(or clipping them), replace the PCM, there's a problem internally on the IAC control circuit. Hope this helps.
JUST to be safe, pull the 3 pin plug on the IAC while the engine is
idling. Does the idle change (speed should increase or start to
fluctuate)? If not, you've got another bad IAC or there's a problem
with the wiring/PCM that's not permitting it to work properly.
The code indicates there is an problem with your Idle Air Control System. Most likely failure is that the IAC system failed. There is an 3 pin from the IAC. Remove it from IAC when your engine is idling.Check whether there is an idle speed change? IF it does not fluctuate then your IAC has gone bad,
The IAC (Idle Air Control) valve controls the idle speed of the engine. At idle the throttle plate is closed, of course. The IAC is computer controlled and allows only a certain amount of air around the throttle plate. This metered air controls the idle speed. The IAC has a "plunger" or "shutter" that moves to open or close the bypass air passageway. The more air the IAC allows around the throttle plate, the higher the idle. The PCM (Powertrain Control Module) uses the IAC valve to keep the idle speed correct with varying engine demands. Can be a three or four wire sensor depending on the model.
The PCM monitors voltages of the IAC circuits and if it detects an incorrect voltage on one or more of the IAC motor circuits it will set P0505. NOTE: Problems with the IAC would only be noticeable at idle or when throttle is closed.
Symptoms may include: * MIL (Malfunction Indicator Lamp) illumination * Engine stalls and may not idle unless throttle is depressed * Intermittently stalls when letting off the throttle * Engine may idle too high
Potential causes of an P0505 code include: * IAC motor connector is damaged (check connector and pins for damage, and moisture) * One or more IAC circuits open or shorted to ground * One or more IAC circuits are shorted to voltage * IAC has failed * PCM has failed
Possible Solutions: This should be a fairly straightforward diagnosis. Start by clearing the fault codes. Then unplug the IAC and start the engine (This may cause other IAC codes to set. Just ignore them for now). If the P0505 code doesn't reset, replace the IAC. It is internally shorting one of the IAC circuits. If the code DOES return after unplugging the IAC and starting the engine, then you know it isn't the IAC motor. Visually check the wiring harness all the way back to the PCM. You may need to visually inspect the harness by removing all the insulation off the wires. It is possible that the wires could be shorting to eachother or to other wires in the harness.
If there are no wiring problems, and the code keeps returning with the IAC unplugged, you can check the PCM by removing the IAC wires from the PCM connector (or clipping the wires in a location where they can be repaired easily) and then start the engine (If you're not sure, don't do it. Take it to a qualified professional). Now if the code doesn't reset there is a problem with the wiring. Check for continuity on all the IAC wires. Any resistance points to a problem. Check for voltage on any(At this point there shouldn't be any voltages on the wires because they're clipped at one end and unplugged at the IAC). Repair as necessary. But if the P0505 code DOES reset after removing the IAC wires from the PCM connector(or clipping them), replace the PCM, there's a problem internally on the IAC control circuit.
Hope this helps (remember to rate and commene this).
This code seems to be "Idle speed control (ISC) system malfunction". Possible causes are wiring,ISC actuator/IAC valve,throttle motor,throttle valve tight or sticking, ECM. Hope this info is useful.
Code P0505 is a problem with the IAC (idle air control) which regulates the idle speed. To check it quickly, disconnect the IAC connection located below the throttle body near the firewall. Start the car and the idle should run around 1300 rpm at idle. If this is the case then the likely cause it a bad idle motor. The cost of a new one is $110 at Pep Boys or $30 at a Pick n Pull. Keep me posted, thx.
P0505 Idle speed continues to vary greatly from the target speed (2 trip detection logic) IAC valve is stuck or closed Open or short in IAC valve circuit Open or short in A/C signal circuit Air intake (hose loose) MARKO
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