1999 Chevy Malibu idle up.

Tiny
TOOMBSEY8
  • MEMBER
  • 1999 CHEVROLET MALIBU
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 130,000 MILES
My engine does not idle up when I turn the a/c on.
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have the same problem?
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No
Friday, May 15th, 2009 AT 9:49 AM

11 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Doese the engine die when you turn the AC on? Has the check engine light come on?
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Saturday, May 16th, 2009 AT 12:39 PM
Tiny
TOOMBSEY8
  • MEMBER
No the car does not die it just acts like it is going to. And the check engine light does not come on.
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Monday, May 18th, 2009 AT 10:48 AM
Tiny
JKIFER632
  • MEMBER
Toombsey8,
I know this post was awhile ago but did you ever fix the prob. Mine is doing the same thing.
This is what I have done so far, Just bought my 1999 Malibu 4cyl. It has a slow idle of 600 rpm's. I have been ready the Malibu forum and I checked the icv it is in working order and I cleaned it and the slot it sits in and cleaned the throttle body and changed the little hose that is under the throttle body and connect to a sensor. I also checked for vacuum leaks with carb cleaner. The car is stll idling at 600 rpm's andis surging.
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Saturday, January 1st, 2011 AT 1:46 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
The IAC is responsible for maintaining the idle. If it is good and you are still getting a surging, you may need to have the PCM checked.
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Saturday, January 1st, 2011 AT 8:18 PM
Tiny
JKIFER632
  • MEMBER
Jacobandnickolas,
What I Dont get is when I put my food on the gas at idle and bring up the RPM's just 100 The surging stops. When I say surging I am talking about in drive with my foot on the brake the car acts like it wants to go. By the way what RPM's should a 1999 Malibu base model 4 cyl. Be idleing at in park? Should the car idle up when I put the AC on? Because it does not.
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Saturday, January 1st, 2011 AT 9:11 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
It should be around 700 + or - 100 RPMs. As far as the AC, yes it should idle up to compensate for the added load from the compressor. Are you sure the IAC is working properly? Also, have you checked for vacuum leaks and the throttle position sensor?
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Saturday, January 1st, 2011 AT 10:43 PM
Tiny
JKIFER632
  • MEMBER
The IAC I took it out and turned the key on and off and it moved in and out. I have checked for vacum leakes and found one and fixed it. How do you check the TPS and where is it?
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Sunday, January 2nd, 2011 AT 3:49 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Here is a good description of it I was able to find. The directions to check it as listed last.

The Throttle Position (TP) sensor is a potentiometer that provides a signal to the PCM which is directly proportional to the throttle plate position. The TP sensor is mounted on the side of the throttle body and is connected to the throttle plate shaft. The TP sensor monitors throttle plate movement and position, and transmits an appropriate electrical signal to the PCM. These signals are used by the PCM to adjust the air/fuel mixture, spark timing and EGR operation according to engine load at idle, part throttle, or full throttle. The TP sensor is not adjustable.

The TP sensor receives a 5 volt reference signal and a ground circuit from the PCM. A return signal circuit is connected to a wiper that runs on a resistor internally on the sensor. The further the throttle is opened, the wiper moves along the resistor, at wide open throttle, the wiper essentially creates a loop between the reference signal and the signal return returning the full or nearly full 5 volt signal back to the PCM. At idle, the signal return should be approximately 0.9 volts.

TESTING

With the engine OFF and the ignition ON, check the voltage at the signal return circuit of the TP sensor by carefully backprobing the connector using a DVOM. Attach the black lead to known good ground, the red lead to terminal B.
Voltage should be between 0.2 and 1.4 volts at idle.
Slowly move the throttle pulley to the Wide Open Throttle (WOT) position and watch the voltage on the DVOM. The voltage should slowly rise to slightly less than 4.8v at Wide Open Throttle (WOT).
If no voltage is present, check the wiring harness for supply voltage (5.0v) and ground (0.3v or less), by referring to your corresponding wiring guide in. If supply voltage and ground are present, but no there is no output voltage from the TP sensor, replace the sensor. If supply voltage and ground do not meet specifications, make necessary repairs to the harness or PCM.

Let me know if it helps.
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Sunday, January 2nd, 2011 AT 7:03 PM
Tiny
JKIFER632
  • MEMBER
I think I just found the prob. In the pic. Look at the rubber 90 it is sucked in when the car is running turn car off and it goes back to norm. What do I call it when I go to the parts store?
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Monday, January 3rd, 2011 AT 1:25 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I can't tell where I'm looking on the engine. Where is that located?
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Monday, January 3rd, 2011 AT 12:32 PM
Tiny
JKIFER632
  • MEMBER
Its on the throttle body next to the iac
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Monday, January 3rd, 2011 AT 2:54 PM

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