Question about 1990 Chevrolet Astro Extended

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1990 chev astro idles high. It has a 4.3 engine. Throttle body

Vacum lines seem to be connected. Checked IAC for ohms 50.1 Could not get the pintle to move inward by hand. Not sure if it should move easy manualy. Any info would help. Thanks

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  • castlemanjoe Jan 03, 2009

    This astro does not have a Vortek eng.

  • Lee
    Lee May 11, 2010

    vortek eng?



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I have a 90 chevy astro with a 4.3l motor it idles high when I start it, ive rebuilt the throttle body changed the iac valve ignition switch and it still does the same thing. anyone have any ideas on whats wrong? if u can help please call or text 5157703344 thank you

Posted on Jan 10, 2016

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I had the same problem with my van and ended up being the TBI base gasket

Posted on Feb 06, 2009


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Extracted from

Code P0507

Possible causes

- Dirty throttle body

- Electric throttle control actuator misadjusted or damaged

- Faulty Electric throttle control actuator

- Intake air leak

- Poor electrical connection to the Intake Air Control (IAC) valve

help.jpg What does this mean?

Tech notes

If there are no intake leaks, clean throttle body, adjust engine idle and erase engine code. If the code comes back you may have to replaced the Electric Throttle Control Actuator (Motor) to repair the problem.

There is a factory service bulletin for the following Chevrolet models:

2006-2008 Chevrolet Trail Blazer

2007-2008 Chevrolet Avalanche

2007-2008 Chevrolet Express

2007-2008 Chevrolet Silverado

2007-2008 Chevrolet Suburban

2007-2008 Chevrolet Tahoe

Chevrolet Factory Service Bulletin OBDII Code P0507

What does this mean?

When is the code detected?

Thi P0507 code sets when the Powertrain Control Module (PCM) detects an engine speed outside of the Idle Air Control (IAC) valve range of control.

Possible symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

- Engine hard to start

- Rough or erratic idle speed

P0507 Chevrolet Description

The Idle Air Control (IAC) valve is a Powertrain Control Module (PCM) controlled stepper motor located on the throttle body. The stepper motor drives a valve pintle which protrudes into a passage that bypasses the throttle plates. The PCM commands the IAC valve pintle to extend to decrease the idle speed. The bypass air flow is reduced and the idle speed decreases as the pintle approaches its seat. The PCM retracts the IAC valve pintle away from its seat to increase the idle speed. The retracting of the IAC valve pintle allows more air to bypass the throttle plates. One of the PCMs uses for the IAC system is to maintain a desired idle speed. This DTC sets when the PCM detects an engine speed outside of the IAC\'s range of control.

Read more:

Jan 11, 2015 | 2001 Chevrolet Blazer

1 Answer

Idle boost servo that is in the A/C on circuit..location ?

There is no such component on that vehicle. You have a fuel injected engine which uses and IAC (idle air control) solenoid mounted on the throttle body to control idle speed. When the A/C is turned on, the ECM sees the request and moves the IAC pintle to allow for a slightly higher idle due to the load of the A/C compressor. There is a small port near the top of the throttle body above the IAC solenoid (air cleaner duct removed) that you can spray some carburetor cleaner into. If a sludge buildup is causing the IAC pintle to stick, this may free it up.

Jun 26, 2014 | 1999 Chevrolet Astro

1 Answer

Labored start and runs while accelerator is pressed. Shuts off immeditely if you release the accelerator.

Check to see if the IAC (idle control valve) is stuck in the bore of the throttle body. you can do this by;

remove the air snorkel from the throttle body.

locate the IAC, it will be round, sometimes silver or gold metal color, an have 4 or five wires on the connector.

You should see a passage in the throttle body near where the IAC is located. look in that passage and see if you can see the pintle of the IAC.

Use a small screwdriver and gently push the pintle of the IAC towards the IAC body. Once it is moved back try starting. Be ready to turn the engine off if the idle goes to high.

If the idle goes up tan remove the IAC (usually two torx screws). Carefully inspect the pintle. If the head looks worn replace it. If it is covered in carbon clean it with carb spray. Also clean out the passage with carb spray. Reinstall the IAC (new or used). Cycle the key a couple of times with out starting the vehicle. This will allow the pintle to move closer to the idle position. Start the vehicle.

Let me know if that works or if it doesn't. I'll be happy to help you further if needed.

Sep 03, 2011 | 1999 Jeep Grand Cherokee

1 Answer

1999 Ram 3500 Wagon with 5.9L has eng Lt on. Idles high at red lights & surges at times. Code scanned is P0505. Do I need idle control valve or computer to make control valve work properly.

The IAC stepper motor is mounted to the throttle body, and regulates the amount of air bypassing the control of the throttle plate. As engine loads and ambient temperatures change, engine rpm changes. A pintle on the IAC stepper motor protrudes into a passage in the throttle body, controlling air flow through the passage. The IAC is controlled by the Powertrain Control Module (PCM) to maintain the target engine idle speed.

At idle, engine speed can be increased by retracting the IAC motor pintle and allowing more air to
pass through the port, or it can be decreased by restricting the passage with the pintle and diminishing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is moved (rotated) in steps, or increments. Opening the IAC opens an air passage around the throttle blade which increases RPM.

The PCM uses the IAC motor to control idle speed (along with timing) and to reach a desired MAP during decel (keep engine from stalling).

The IAC motor has 4 wires with 4 circuits. Two of the wires are for 12 volts and ground to supply electrical current to the motor windings to operate the stepper motor in one direction. The other 2 wires are also for 12 volts and ground to supply electrical current to operate the stepper motor in the opposite direction. To make the IAC go in the opposite direction, the PCM just reverses polarity on both windings. If only 1 wire is open, the IAC can only be moved 1 step (increment) in either direction. To keep the IAC motor in position when no movement is needed, the PCM will energize both windings at the same time. This locks the IAC motor in place.

In the IAC motor system, the PCM will count every step that the motor is moved. This allows the
PCM to determine the motor pintle position. If the memory is cleared, the PCM no longer knows the position of the pintle. So at the first key ON, the PCM drives the IAC motor closed, regardless of where it was before. This zeros the counter. From this point the PCM will back out the IAC motor and keep track of its position again.

When engine rpm is above idle speed, the IAC is used for the following:
  • Off-idle dashpot (throttle blade will close quickly but idle speed will not stop quickly)
  • Deceleration air flow control
  • A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)
  • Power steering load control
The PCM can control polarity of the circuit to control direction of the stepper motor.

  1. First, try removing the IAC Valve, and cleaning the valve and the opening in the throttle body where the IAC Valve installs using Carburetor Cleaner. Ensure that the IAC Valve hole in the throttle body is not clogged, and is free from carbon deposits, etc. Have the ECM reset and check for the problem again.
  2. If the Check Engine Light comes back on, replace the IAC Valve. Have the ECM reset and check for the problem again.
  3. If the Check Engine Light still comes on, although highly unlikely, you may have a clogged throttle body, faulty wiring or connector, or faulty ECM (very unlikely since the vehicle runs).

Apr 13, 2011 | 1999 Dodge Ram

3 Answers

Computer code p0505 -running at high idle

Hi, not sure which engine you have so I can't be precise, but here is what I recommend. Remove the idle air control valve and check the valve seat for blockage. If dirty, clean both the passages and the valve, reinstall and see if that resolves the code. If it isn't blocked or dirty, run the tests below using a volt/ohmmeter. The primary test to run is step 8. If the valve fails step 8, replace the valve. If it passes, then check the PCM reference voltages in step 7. Let me know if you have questions.


TESTING Conclusive testing of this component requires the use of special, factory-supplied equipment and is not included here. The tests below will provide valuable information regarding condition of the IAC motor and require only a VOM.

  1. Ignition must be OFF .
  2. Disconnect the IAC motor connector.
  3. Disconnect the PCM harness connector(s).
  4. Measure the resistance of the four IAC motor wires between the motor connector and the PCM connector. Refer to the illustrations for wire colors.
  5. Resistance should be under 5.0 ohms. Replace any wire with a higher resistance.
  6. Check for resistance between each motor lead and ground. Replace any wire with resistance under 5.0 ohms.
  7. Remove the ASD relay from the PDC (location is shown on the underside of the PDC cover. Connect a jumper between cavity 30 and 87 . Turn the ignition ON . Measure the voltage at each of the driver wires. Voltage should not exceed 1.0 v.
  8. With the ignition OFF and the IAC and PCM connectors detached, measure the resistance between each driver wire and ground. Resistance must be above 5.0 ohms in each case.

Fig. IAC motor assembly


Fig. IAC motor electrical connector pinouts


Fig. IAC motor and driver circuits

The IAC motor is located on the rear of the throttle body secured by two Torx® screws.

  1. Disconnect the negative battery cable.
  2. Remove the air cleaner assembly.
  3. Unplug the IAC motor connector.
  4. Remove the two mounting Torx® screws.
  5. Remove the IAC motor from the throttle body.

WARNING When the IAC motor is removed from the throttle body, do NOT extend the pintle more than 0.250 inch (6.35mm). If the pintle is extended more than this amount, it may separate from the IAC motor and the motor will have to be replaced.

To install:
  1. Install the IAC motor in the throttle body.
  2. Tighten the mounting bolts to 60 inch lbs. (7 Nm).
  3. Plug the IAC electrical connector in.
  4. Install the air cleaner assembly.
  5. Connect the negative battery cable.

Fig. IAC motor mounting screws (arrows)

Feb 25, 2011 | 1999 Dodge Ram

1 Answer

Will not idle, will run if you push on the gas and hold it. No engine light indicator

you need to clean your idle air control valve ( or replace it) Spray carb cleaner does a nice job of cleaning it.

This tutorial is from


The Idle Air Control (IAC) is a bi-directional motor driven by two coils. The purpose of the IAC valve is to control engine idle speed, while preventing stalls due to changes in the engine load. The IAC valve, mounted in the throttle body, controls bypass air around the throttle plate. The PCM controls engine idle speed by adjusting the position of the IAC motor pintle. The PCM pulses current to the IAC coils in small steps (counts) to extend the pintle into a passage in the throttle body to decrease air flow. The PCM reverses the current pulses to retract the pintle, increasing air flow. This method allows highly accurate control of idle speed and quick response to changes in engine load. If RPM is too low, the PCM will retract the IAC pintle, resulting in more air being bypassed around the throttle plate to increase RPM. If the RPM is too high, the PCM will extend the IAC pintle, allowing less air to be bypassed around the throttle plate, decreasing RPM.

0900c15280217cd2.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig. Typical Idle Air Control (IAC) valve components
During idle, the proper position of the of the IAC pintle is calculated by the PCM based on the battery voltage, coolant temperature, engine load and engine RPM. If the RPM drops below a specified value, and the throttle plate is closed (TP sensor voltage is between 0.20-0.74), the PCM senses a near stall condition. The PCM will then calculate a new IAC pintle position to prevent stalls.
If the IAC valve is disconnected and reconnected with the engine running, the idle RPM will be wrong. In this case, the IAC has to be reset. The IAC resets when the ignition switch is cycled ON and then OFF . When servicing the IAC, it should be disconnected or connected with the ignition switch OFF in order to keep from having to reset the IAC valve.
The position of the IAC pintle affects engine start up and the idle characteristics of the vehicle. If the IAC pintle is fully open, too much air will be allowed into the manifold. This results in high idle speed, along with possible hard starting and a lean air/fuel ratio. A Diagnostic Trouble Code (DTC) may set. If the IAC pintle is stuck closed, too little air will be allowed in the manifold. This results in a low idle speed, along with hard starting and a rich air/fuel ratio. Again, a Diagnostic Trouble Code (DTC) may set. If the IAC pintle is stuck part way open, the idle may be high or low and will not respond to changes in engine load.


As with most all engine control sensors used in your vehicle, a thorough and proper test can only be performed by a qualified technician using a scan tool to read the data stream from the PCM. There are a few items a non-professional should check before taking the vehicle to a qualified technician for diagnosis and repair.

Check for a poor connection at the PCM or IAC motor. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connection. Inspect for a damaged wiring harness, especially if heavy work has recently been performed (intake manifold removal, engine removal, etc.) where the throttle body has been disturbed. Inspect for a restricted air intake system. Check for a possible collapsed air intake duct, restricted air filter element or foreign objects blocking the air intake system. Inspect the throttle body. Check for objects blocking the IAC passage or throttle bore. Excessive deposits, especially on high-mileage engines, can build up in the IAC passage and on the IAC pintle. Excessive deposits can also build up on the throttle plate, so check for a sticking throttle plate. Check for vacuum leaks such as disconnected hoses, leaks at the EGR valve and EGR pipe to the intake manifold, leaks at the throttle body, faulty or incorrectly installed PCV valve, leaks at the intake manifold brake booster hose connection, etc.


  1. Disconnect the negative battery cable.
  2. Detach the electrical connector from the IAC valve.
  3. Remove the 2 attaching screws and remove the IAC valve from the engine. Remove the O-ring from the housing.

To install:

0900c15280217cd3.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig. The Idle Air Control (IAC) valve is mounted on the throttle body-3.8L (VIN K) engine shown, others similar

NOTE Before installing a new IAC valve, measure the distance that the valve is extended. The measurement should be made from the motor housing to the end of the valve cone (pintle). The distance should be no greater than 1 1 / 8 inch (28mm). If the pintle is extended too far, adjustment is required, otherwise damage may occur when the IAC valve is installed. Adjust the IAC valve by compressing the pintle to achieve the correct length.

  1. Use a new O-ring, install the IAC valve and tighten the retaining screws to 18 inch lbs. (2 Nm).
  2. Attach the electrical connector.
  3. Connect the negative battery cable.
  4. The PCM will reset the IAC valve the next time the ignition switch is turned ON and then OFF .
  5. Start the engine and allow to warm to operating temperature to check idle quality.

Oct 13, 2010 | 2000 Pontiac Grand Prix

2 Answers

The engine races and the temp drops. I asked the question yesterday and was told to check the idle air control. There is not one on my model. anyone?

I'm assuming that you have idle high in the engine, and IAC fault code.


Know Your Circuit:
* In order to regulate the air entering into the engine, the Engine Control Module (ECM) uses an Idle Air Control (IAC) Valve.
* To raise the idle rpm, the ECM handles the pintle inside the IAC valve away from the throttle body seat.
* This enables additional air to bypass through the throttle blade.
* To lower the rpm the ECM controls the pintle towards the throttle body seat.
* This successfully reduces the amount of air bypassing the throttle blade.
* A scan tool will note the IAC valve pintle position.
* The greater the count, the greater air is allowed to bypass the throttle blade.
* This DTC ensures whether a low idle condition exists as defined as 100 rpm below the desired idle rpm.

Pre -requisites For Setting the DTC:
· No intrusive tests are active.
· DTC(s) P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P1133, P1134, P0171, P1171, P0172, P0201, P0202, P0203, P0204, P0300, P0336, P0337, P0341, P0342, P0351, P0352, P0402, P0404, P1404, P0405, P0406, P0443, and P0502 are not set.
· Engine is running > 60 seconds.
· Barometric Pressure (BARO) is > 72 k Pa (10.4 psi).
· Engine Coolant Temperature (ECT) is > 60°C (140°F).
· Ignition voltage ranges between 11 and 16 volts.
· The Intake Air Temperature (IAT) is > -20°C (-4°F).
· Manifold Absolute Pressure is less than 60 k Pa (8.7 psi).
· IAC valve is fully opened.
· All of the above must be met for more than 5 seconds.


Diagnostic Tools:
* Probe the IAC valve electrical connection for proper mating.
* Examine the wiring harness for damage.
* See whether the throttle stop screw shows signs of distortion.
* Also inspect the throttle linkage for signs of binding or excessive wear and tear.
* The following conditions may be created by a slow or unsteady idle:

1) Fuel system very high or low.
2) Foreign material in the throttle body or in the induction system bore
3) A leaking or restricted intake manifold.
4) Excessive engine overloading. Check for seized pulleys, pumps, or motors on the accessory drive
5) Excess engine oil.

DTC P0505 Idle Air Control Valve (IACV) Circuit Fault






Hope this help.

Apr 20, 2010 | GMC Envoy Cars & Trucks

1 Answer

4.3 TBi code Z cuts out at idle. Please Help!!

Try cleaning the IAC VALVE in the opening in the throttle body with throttle body cleaner,clean well or replace IAC VALVE ( idle air control ) .

Mar 27, 2010 | 1992 GMC Jimmy

2 Answers

I have a 1997 monte carlo and i recently cleaned my throttle body and egr ports as well as put new gaskets on them. now when i start it up i have a high idle. changed my throttle position sensor because i...

U do have a vacum leak, that sound u hear is the problem. Normaly a Mechanic would start the vehical and go under the hood and listion real gone or use a can of carb cleaner and spray around the intake area and over the vacum lines..Now I did say a real Mechanic would done this...

Mar 10, 2010 | 1997 Chevrolet Monte Carlo

1 Answer

I need to know where the idle adjustment screw is on a 92 Saturn SL1 and what wrench to use.

its located on the throttle body connected to your air intake manifold where your throttle cable connects on the throttle body there is a adjustment screw connected there

Nov 03, 2009 | 1992 Saturn SL1

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