What does a IAC Valve do to my 2002 VW Derby - Volkswagen Cars & Trucks

Clean the IAC motor and inside the throttle body. This will fix your problem.

Sounds like a possible idle air control problem (IAC) The smoke probably has nothing to do with the idle problem. Possible valve cover leak??

Hi.

If you are referring to P1507 (poor idle), check the IAC valve. That is usually behind the problem. Clean IAC valve using carb cleaner Check the parts comprised in IAC system (valve, connector, wiring, solenoid). Use the carb cleaner also to clean throttle body. Check that everything is OK in the air intake (no broken parts) and try replacing filter.

Sometimes it is difficult to test in full the IAC valve. Try performing the general testing described summarily here. If that does not reveal any problem but still is very low, clean throttle body, MAF and air intake temperature sensors, replace air filter, check air intake and finally get back to IAC valve and replace it.

Below a diagram showing the IAC valve in the 4 cylinder engine. Position is slightly different in the six cylinder:

code P0128 ECT ( electronic coolant temperature ) engine temperature to low ( replace thermostat ).

code P0300 engine miss fire detected ( replace spark plugs and spark plug wires )

code P0506 IAC ( idle air control ) system idle to low ( clean the IAC valve if problem persists replace the IAC valve )

Operation

The Idle Air Control (IAC) valve controls the amount of air that bypasses the throttle valve, which controls the engine idle speed. The IAC valve consists of windings, an armature, a return spring, and a rotary slide. The engine control module (ECM) pulses the voltage to the winding, the opposing forces on the armature by the return spring cause it to maintain a fixed position, adjusting the amount of bypass air to maintain the correct idle speed.

Removal & Installation

1. Turn the ignition switch to the OFF position.
2. Disconnect the idle air control valve harness electrical connector.
3. Using a suitable tool, remove idle air control valve.
4. Installation is in reverse order of removal.

Testing

Checking Idle Air Control Valve (IAC) Triggering

1. Check IAC valve is electrically OK.
2. Slide up boot on the IAC valve connector.

Fig. IAC Connector

1. Use scan tool 'Output Diagnostic Test Mode' function 03 to trigger the IAC valve - N71.
2. Connect VAG 1527B voltage tester, or equivalent, between terminal 1 and engine ground (GND). Voltage tester must flash.
3. Connect VAG 1527B voltage tester, or equivalent, between terminal 2 and battery positive voltage (B+). Voltage tester must light up.
4. If specified results are not obtained:
   1. Connect VAG 1598/19 test box, or equivalent, to ECM harness connector.
   2. Check the wiring between harness and connector terminal 1 (in engine compartment) to test box socket D11 . Then check the wiring between harness connector terminal 2 and test box socket D9 using wiring diagram. Repair as necessary.
   3. If the wiring is okay, but triggering still does not occur, replace the ECM.
   4. If the triggering signal and the wiring are okay and the valve does not react, replace the IAC valve.
   
   

Checking Mechanical Function

1. Remove the idle air control (IAC) valve.
2. Visually check the surface of the rotary slide (arrow) for signs of wear.

Fig. Showing the IAC Valve

WARNING Do NOT check for ease of movement by prying on the rotary slide with a screwdriver or other tools that could cause scratching or other damage.

1. Reconnect the IAC valve, while still removed, to the harness connector.
2. Use scan tool 'Output Diagnostic Test Mode' function 03 to trigger IAC valve - N71.
3. Check whether rotary slide moves freely from stop to stop.
4. If there are signs of scoring, or if the rotary slide does not move freely in both directions, replace the IAC valve.
5. If the IAC valve does not respond (not triggered) during the Output Diagnostic Test Mode, check triggering.

Resistance Test

1. Remove the idle air control valve harness connector.
2. Use a suitable Digital Multimeter (DMM) to measure the resistance between the 2 terminals of the idle air control valve.
3. The correct measurement should be 7-11 ohms. If not, replace the idle air control valve.

NOTE At room temperature, the resistance value will be lower. The resistance value will be higher if the Idle Air Control (IAC) valve is measured at under-hood operating temperatures.

1. Reconnect the idle air control valve harness connector.
2. The idle air control valve should hum and vibrate slightly when the ignition is turned 'ON'. If not, the ECM or harness may be defective.

Testing with VAG1551:

1. Remove the idle air control valve harness connector.
2. Connect the VAG 15278 LED tester to terminals 1 and 2 of the harness connector using the jumpers from VW 1594 adaptor kit.
3. Turn ignition ON, perform steps from output DTM (Diagnostic Test Mode) to activate the IAC valve (N71) LED tester must blink.
4. If tester does not blink, check wiring using VAG 1598 pin out box, electrical checks, step 26. Repair as necessary.
5. If wiring is okay, replace the ECM.
6. If LED tester blinks but the IAC valve does not operate, replace the IAC valve.

THE IAC VALVE (IDLE AIR CONTROL) MAYBE DIRTY OR STICKING,TRY CLEANING THE THROTTLE BODY WHERE IAC VALVE IS. IF THAT DOES NOT WORK REPLACE IAC VALVE.

If it's not idling and has problems starting, it's probably the IAC motor. It's located on the throttle body. Follow the airfilter box all the way to the engine, where the rubber flex hose attaches. The throttle body should be the first aluminum part you come to. Attached to the side you'll find small little aluminum part with a small wire harness attached. Unplug it, take the IAC motor off and clean inside with carb cleaner. This should fix the problem with the idle.

The idle air control (IAC) valve assembly on a combustible engine monitors and manipulates the amount of controlled air moving around the throttle plate. The IAC valve is managed by the electronic control module (ECM) of the engine, which calculates the position of the IAC valve. Voltage pulses called counts extend and retract an internal conical-tipped shaft called a pintle inside the IAC valve. When the pintle is extended, the cone-shaped tip positions itself closer to the air inlet and restricts the amount of air allowed to pass through the throttle, building up more air around the throttle plate to increase the rpms of the engine. When the pintle is retracted, it moves away from the inlet and allows more air into the throttle away from the throttle plate, decreasing the rpms. The IAC valve operates and adjusts constantly while the engine is running to help prevent the engine from stalling or surging. This will not cause the engine to misfire!! Hopefully this helps

you may have a problem with your iac valve it controls your idle. get so throttle body cleaner and clean the throttle body and spray into the little hole on the side of the butterfly that leads to the iac valve. if that does not work you may have to replace it.

1. will it stay running if you foot is sligtly on the gas.
if so common problem it the IAC valve located on top of the throttle body. it controls ait into the engine when throttle is closed.
2. do you hear loud fog horn like sound or hissing. this could indicate a vaccum leak.
3. are there any performance problems while driving.

my best guess would be the IAC (idle air control) valve