Question about 1994 Pontiac Firebird

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High idle i bought new lines and a tps,map sensor and a iac and at park its idles at 1500 rpm

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Richard Scordino

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Clean the throttle body inside to make sure the throttle plate closes properly. also clean the mass air flow sensor cross wires inside it's bore. If there are no vacuum leaks, this may help

Posted on Jun 06, 2009

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Why does my 2004 buick rendezvous idle at 3000 rpm and put in gear it drops to 1500 rpm and shifts hard while driving due to high engine speed?


Stuck throttle plate . gummed up with varnish or a problem with IAC valve . IAC - idle air control valve ! Videos on youtube , how they work how to clean . Idle Air Control Valve Could have unmetered air entering the engine pass the MAF sensor , a bad MAP sensor ! I would check the throttle plate first , if dirty clean it . Then check IAC valve if not the throttle plate . GM Idle Air Control IAC Function Diagnostics and Repair

Dec 14, 2016 | Buick Cars & Trucks

1 Answer

2003 impala intermittent high idle with high iac count iac tested good


Before buying a ECM for the car I would do a smoke test on the vacuum line to be sure there is no leaks and causing the idle to very. Hope this helps.

Apr 17, 2017 | 2003 Chevrolet Impala

2 Answers

Stalls while in drive with foot on brake , changed MAP Sensor, Crank Shaft Sensor , Distributor, Fuel Pump, Fuel Filter , have ran out of ideas


I would check the IAC motor or idle air control motor, heres a little info.about the part.Stratus Sedan, 1999-2005 Idle Air Control Motor

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Description & Operation

Not for Dodge Stratus Sedan
The idle air control motor (IAC) attaches to the throttle body. It is an electric stepper motor. The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load, coolant temperature or barometric pressure changes. The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The idle air control motor pintle protrudes into the air bypass passage and regulates airflow through it.
The PCM adjusts engine idle speed by moving the IAC motor pintle in and out of the bypass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning).

0996b43f8020234f.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig.

Not for Dodge Stratus Sedan
When engine rpm is above idle speed, the IAC is used for the following functions:


Off-idle dashpot 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)
The idle air control motor (IAC) attaches to the throttle body. It is an electric stepper motor. The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load, coolant temperature or barometric pressure changes. The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The idle air control motor pintle protrudes into the air bypass passage and regulates airflow through it.
The PCM adjusts engine idle speed by moving the IAC motor pintle in and out of the bypass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning).

21180_cdia_g257.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig.

When engine rpm is above idle speed, the IAC is used for the following functions:


Off-idle dashpot 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)
Target Idle
Target idle is determined by the following inputs:


Gear position ECT Sensor Battery voltage Ambient/Battery Temperature Sensor VSS TPS MAP Sensor
Target idle is determined by the following inputs:


Gear position ECT Sensor Battery voltage Ambient/Battery Temperature Sensor VSS TPS MAP Sensor


Removal & Installation

  1. Disconnect the negative battery cable.
  2. Disconnect the IAC electrical connector.
  3. Remove the IAC mounting screws.
  4. Remove the IAC.

To Install:
  1. Install the IAC to the throttle body.
  2. Tighten mounting screws to 5.1 Nm (45 inch lbs.) torque.
  3. Attach electrical connector to the IAC.
  4. Connect the negative battery cable.

    0996b43f80202350.jpg enlarge_icon.gifenlarge_tooltip.gif

    Fig.


  1. Disconnect the negative battery cable.
  2. Disconnect the IAC electrical connector.
  3. Remove the IAC mounting screws.
  4. Remove the IAC.

To Install:
  1. Install the IAC to the throttle body.
  2. Tighten mounting screws to 5.1 Nm (45 inch lbs.) torque.
  3. Attach electrical connector to the IAC.
  4. Connect the negative battery cable.

May 11, 2012 | 2000 Chrysler Cirrus

2 Answers

99 Cavalier idle surge and excessive idle rpm.


Check your vacuum lines for leaks. Symptoms suggest vacuum leak.

Nov 20, 2017 | 1999 Chevrolet Cavalier

1 Answer

High idle on 97 silverado


sounds like the idle air is gone

Apr 10, 2010 | 1997 Chevrolet K1500

2 Answers

I have a 1990 Chevy 1500 SS truck with a 454ci. that has an idle


You don't have to try both, but...If you can get a scanner hooked up, you can see the TPS move as you depress the throttle, and verify if it is good or bad. The IAC can also be viewed with a scanner, and they get gummed up, and most can be cleaned.
Also, a bad temperature sensor can cause a high idle if it thinks it's real cold out.
Also, a bad power steering pressure switch can cause a high idle.
All of these can be looked at with a scanner!

Mar 06, 2010 | 1986 Chevrolet K1500

1 Answer

Idle speed high


Sounds like the tps (throttle position sensor) is either defective, or out of adjustment. Need an oscilloscope to check, so see a mechanic. Could also be vacuum leak. check lines for cracks and leaks

Oct 19, 2009 | 1990 Isuzu Trooper

1 Answer

Idle too high +goes higher when put in gear (manual transmision


IAC valve problem. Nissan has a updated harness (with one way diode inside of the harness) to prevent backfeeding for the IAC valve and a new IAC valve also gets installed. That's where I would look. IAC valve or "idle air control" valve.

Aug 23, 2008 | 1998 Nissan 200SX

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