Question about 1985 Porsche 928

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MY 85 928 won't hold an idle. I thought it was the air idle control valve but found the car had a Bosch 'Air Slide' instead. This was bench tested and is working......is there also an air idle control valve on this car? If so, where is it?

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Not sure, but have you checked ALL of your vacuum lines for cracks/leaks - most likely cause is an air leak in vacuum lines or fuel inlet.

Posted on Mar 29, 2014

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I replaced the fuel pump. but my car wont stay running unless i hold down the gas pedal. when i let off the gas it dies. what could be the problem?


The idle air control valve or the idle air control valve passages . Or you have a vacuum leak . Is your check engine light on ? Idle Air Control Valve . While there on you tube check out how to test one an how to clean air passage .
Sensor/System
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Test for conditions which cause an incorrect idle speed.


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Throttle body tampering, excessive deposits, or damage. Refer to Fuel System Description .


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Restricted air intake system


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Large vacuum leak


?€¢
Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the mass air flow (MAF) sensor and the throttle body.


?€¢
Inspect crankcase ventilation valve for proper operation.


?€¢
Inspect the throttle position (TP) sensor and related wiring. Refer to DTC P0123 .


?€¢
Monitor the 24X crank sensor and the CMP sensor present parameters on the scan tool. If both are not responding, test the sensor feed circuit. Both sensors use a separate feed circuit but are internally connected to power. Test all CKP sensor A and CMP sensor circuits for intermittents. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.


?€¢
Monitor the 3X parameter on the scan tool. If the 3X is not responding, inspect the CKP sensor B and circuits for intermittents. Inspect the ignition control (IC) circuit, IC timing control circuit, low resolution engine speed signal circuit and the low reference circuit for intermittents. If these circuits become open, or shorted may not set a DTC immediately, but are capable of causing driveability complaints. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.


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Test the exhaust gas recirculation (EGR) system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .


?€¢
Inspect the transaxle range switch input with the vehicle in drive and the gear selector in drive or overdrive.


Dec 08, 2015 | 2003 Chevrolet Impala

1 Answer

2000 Malibu won't idle unless u hold gas a lil


Is the check engine light on ? Is the throttle body clean ? Is the idle air control valve working ?

Jun 30, 2013 | Cars & Trucks

1 Answer

94 nissan altima won't start and iddle after cleaning IACV valve


An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The cars computer or PCM (powertrain control module) receives information from various sensors and will output signals to adjust the idle air control motor in or out to adjust engine idle speed by controlling engine idle air. An idle air control motor can fail one of two ways, either the motor short circuits and stops working or the motor will develop high resistance and cause the idle air control motor to react slowly, either failure can cause the engine to stall at idle. When a trouble code scan is performed it sometimes won't always detect a failed or weak idle air control motor.

Oct 08, 2012 | Nissan Altima Cars & Trucks

1 Answer

Won't idle with idle air control valve plugged in


Usually a sign the valve is faulty or the throttle body needs to be cleaned.

Sep 12, 2012 | 2002 Suzuki Grand Vitara

1 Answer

High idle after engine is warm. nothing is sticking with linkage.1992 chev k1500 5.7


Make sure the idle screw was not turnned causeing tps sensor to read over the spec limit, the next then is to make sure the idle air control valve is working , a bad valve will cause this problem and last is the stepper motor that controls the idle. some of these around this year used steeper idle control motors instead of idle air control valves and in turn the stepper motor is bad it will hold the throtle plate open to much causing the tps reading to be wrong triggering the engine light to come on. the steeper motor will be boltted to side of the throtlebody and theres a small arm to the throtle linkage. i will enclose a stepper motor picture and an idle air valve to show you, but this sounds like the tps is out of range due to this. the last thing is to make sure there are no vacuum leaks, spray crab cleaner around throtlebody base gasket and also the intake mounting gasket and see if the idle changes is so theres a vac leak in that area. good day. okay just did a little research and this truck does have a idle air control valve, the picture is encolsed and is screwed into throtlebody, check that and for vacuum leaks, make sure tps is good sometime it will test good when testing and go bad when it wants, you could have a bad tps and idle air control valve also.11_27_2011_9_27_54_pm.jpg

Nov 24, 2011 | 1992 Chevrolet K1500

1 Answer

I have a 1987 Ford Tempo. The car has a hard time starting. When I get it start it won't Idle. You have to hold the gas pedal down and even then the car wants to surge. What do you think the problem...


This may be as simple as a bad idle air control valve which controls the idle , it may also be a weak fuelpump, i would first have the fuel pressure tested to make sure its good, then i would clean the throtlebody with cleaner and replace the idle air valve. the engine it must not be skipping due to a sparkplug or sparkplug wire, there are many things that will cause this. you will neeed to do some checking and make sure the engine is operating good, is you have a bad idle air control valve you should be able to hold the gas pedal a little and keep the engine running after a few minutes the engine should run okay with you holding the pedal , keep in mind this is a 1987 tempo i dont know how many miles are it or if the engine is in need of work but if this is whats happening then try cleaning the throtle and replacing the iac valve. good day.

Sep 24, 2011 | Ford Tempo Cars & Trucks

1 Answer

When the car starts cold it starts and idle goog for a few seconds after it idle drops to 0 then cuts off


Idle air control valve is probably playing up or leaks in air intake system from air filter box to inlet manifold.

Idle air control valve can be found on inside of inlet manifold. Take air cleaner parts off and there should be a small groove somewhere. squirt out with brake claner / degreaser

Mar 01, 2011 | Chevrolet Silverado 1500 Cars & Trucks

1 Answer

When i turn on the ac the idle goes low and the the car vibrates. When i turn off the ac the car stop vibrating.



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.



0900c152801c00a1.jpg enlarge_icon.gifenlarge_tooltip.gif

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.



0900c152801c00a2.jpg enlarge_icon.gifenlarge_tooltip.gif

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.

Feb 15, 2011 | 2000 Volkswagen Jetta TDI

1 Answer

Idle speed control


Hmmmmmm.... seems to me you have a completely different problem since you've verified the idle control valve is working. What controls the idle control valve?... AH!... the ECU!... is the wiring between the ECU and the Idle Control Valve in good condition and making good connections? mmmmmmmmm... then I'd say you have a defective computer (ECU). Here's something you might try. Disconnect the battery connection cables from the battery... touch them together (cables + & -) for thirty seconds. Reconnect the cables to the battery and see what happens. Sometimes there's 'GARBAGE' stored in the ECU memory and interferes with the normal operation of components. If nothing changes, you'll need to start testing (bench testing) components (idle speed control actuator (make sure it's not 'sticking'). check for vacuum leaks.... thoroughly inspect intake air hoses & vacuum hoses... inspect all EMS (Engine Management System) connectors for any signs of corrosion or mal-connections (male & female pins). The problem may simply be electrical contacts/connections.. .then again, it could be mechanical.

May 18, 2009 | 1994 Hyundai Excel

4 Answers

1987 bmw 325 idles rough


On the 325 series I have worked on (your year, make, model), I have found that idling issues like you describe are the result of a defective oxygen sensor. Replace the oxygen sensor with a Bosch unit. That should take care of your issue.

Apr 11, 2009 | 1987 BMW 3 Series

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