How to check the resistance on the iac in a 2000 acura ti?

Hope this helps. you can see the intake air duct--throttle body--iac valve.

check that the HT leads are separated and not touching each other. The misfire may be simply the spark being inducted into the plug with the least resistance and is random and that is what is setting off the light.

Try cleaning the throttle body and Idle controll valve with seafoam or gummout spray and if it still stalls replace the Idle Controll (IAC) valve.
If the check engine light is on and this is a USA car, the repair may be covered under a warranty extension this car has till 150,000. This video could be helpful...


Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

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Try cleaning the throttle body and Idle controll valve with seafoam or gummout spray and if it still stalls replace the Idle Controll (IAC) valve.

If the check engine light is on and this is a USA car, the repair may be covered under a warranty extension this car has till 150,000. This video could be helpful...

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

First check for a vacuum leak. Any small loose hoses in the engine compartment? If not, suspect the idle air control valve. I have pasted test procedures for the iac below. Be careful not to confuse the tps with the iac. The tps is centered on the ybro5ttle body. The iac is more on the perimeter. An additional test I do after checking the valve is to plug it back in while it is still off the throttle body and verify that it actuates a little when the key is turned on. It should back up a tad to allow idle air through the passage for starting.

TESTING
Disengage the IAC electrical connector.Using an ohmmeter, measure the resistance between IAC terminals A and B. Next measure the resistance between terminals C and D.Verify that the resistance between both sets of IAC terminals is 20-80 ohms. If the resistance is not as specified, the IAC may be faulty.Measure the resistance between IAC terminals B and C. Next measure the resistance between terminals A and D.Verify that the resistance between both sets of IAC terminals is infinite. If the resistance is not infinite, the IAC may be faulty.Also, with a small mirror, inspect IAC air inlet passage and pintle for debris. Clean as necessary, as this can cause IAC malfunction.


Fig. Fig. 2: Using an ohmmeter, backprobe terminals of the TPS sensor to check for proper resistances



Fig. Fig. 3: The TP sensor and IAC sensor are usually located at the side of the throttle body



Fig. Fig. 4: Idle Air Control (IAC) valve wiring and terminal identification
REMOVAL & INSTALLATION

Disconnect the negative battery cable.Disengage the electrical connection.Remove the IAC valve. On thread-mounted units, use 1 1 / 4 in. (32mm) wrench and on flange-mounted units, remove the screw assemblies.Remove the IAC valve gasket or O-ring and discard it.To install:
Clean the old gasket material from the surface of the throttle body assembly on the thread mounted valve. On the flange-mounted valve clean the surface to ensure proper O-ring sealingInstall the valve with a new gasket or O-ring. Tighten the thread mounted assembly 13 ft. lbs. (18 Nm) and tighten the flange mounted attaching screws to 28 inch. lbs. (3 Nm).Engage the electrical connector to the IAC valve.Connect the negative battery cable.

P0505 - IAC (Idle Air Control) System Malfunction

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).

First check to make sure the throttle return springs are closing the throttle. If that's good, the problem is likely a bad idle air control valve/motor. Take the valve out and check for obstructions in the port that could keep the valve from closing. Then, if you have an ohmmeter, you can run these checks on the valve:

IAC location:

Remove IAC, check for obstructions in passage, run electrical tests

1. Disengage the IAC electrical connector.
   
2. Using an ohmmeter, measure the resistance between IAC terminals A and B . Next measure the resistance between terminals C and D .
3. Verify that the resistance between both sets of IAC terminals is 20-80 ohms. If the resistance is not as specified, the IAC may be faulty.
4. Measure the resistance between IAC terminals B and C . Next measure the resistance between terminals A and D .
5. Verify that the resistance between both sets of IAC terminals is infinite. If the resistance is not infinite, the IAC may be faulty.
6. Also, with a small mirror, inspect IAC air inlet passage and pintle for debris. Clean as necessary, as this can cause IAC malfunction.

This sounds like a faulty idle air control valve (IAC). A leaking vacuum line could also cause these symptoms. Check for vaccum leaks, and then for faulty connections at the IAC. It is located near or in the throttle body. If no leaks are found, disconnect wiring to IAC. If behavior is the same with IAC disconnected, the IAC probably needs replacement. Sometimes they can be cleaned, but this usually doesn't help for long. You can probably also get resistance specs for the IAC from the dealer and check the IAC resistance with a ohmmeter to see if it is OK. If the IAC is OK and there are no obvious vac. leaks, you might have an intake manifold leak. This can be tested by aiming an UNlit propane torch at the base of the intake at different points with engine running. If the idle increases in response, the intake is probably leaking. This is unusual on Hondas/Acuras, though.

it is on the throttle body.
http://www.acura-legend.com/vbulletin/f13/diy-iac-cleaning-85010/

Check for vacuum leaks and test the idle air conrtol valve.

TESTING

See Figure 2

1. Disengage the IAC electrical connector.
2. Using an ohmmeter, measure the resistance between IAC terminals A and B. Next measure the resistance between terminals C and D.
3. Verify that the resistance between both sets of IAC terminals is 20-80 ohms. If the resistance is not as specified, the IAC may be faulty.
4. Measure the resistance between IAC terminals B and C. Next measure the resistance between terminals A and D.
5. Verify that the resistance between both sets of IAC terminals is infinite. If the resistance is not infinite, the IAC may be faulty.
6. Also, with a small mirror, inspect IAC air inlet passage and pintle for debris. Clean as necessary, as this can cause IAC malfunction.

Do It Yourself Diagnosis and Repair