Question about 1999 Saturn SL

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Saturn 1999 sl Engine has a high idle speed. How do I find, replace, inspect IAC?

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  • Anonymous Mar 31, 2010

    I removed the IAC and the TPS to inspect and clean. The IAC was chared so I clean it with carb cleaner. I replaced both but the engine still idles high. I'm thinking I will have to replace the IAC.



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The Idle Air Control valve is located on the throttle body. If you follow the intake tube from your air filter all the way back to the intake manifold, where the intake tube connects to is the throttle body. Remove the intake tubing and you can see the throttle body.

There are two sensors on the throttle body and a vacuum line. You'll see two harnesses going to the throttle body, one is the IAC.

However, a quick diagnostic check can be done without touching the throttle body to confirm your problem. If the car has a normal idle when initially started but then rises to a higher idle and stays there BUT then if you were to shut the car off and restart it and it comes back to normal that is the Throttle Position Sensor (TPS). This is also located on the throttle body (the other sensor to the IAC). If it is the IAC it will be high and maybe fluctuate a bit.

Posted on Mar 31, 2010

Testimonial: "I was the one who listed this problem. Thanks a TON for the info. Now, I'll try to fix it. The ultimate check is if if idles normally."

  • 1 more comment 
  • Jta91
    Jta91 Mar 31, 2010

    How high of an idle are we talking about here? Anything over 2K RPMs means there is a vacuum leak. The 99 SL1's have a problem with the intake manifold gasket leaking at the #1 Cylinder. The reason is from a factory robotic mistake and it creased that edge when it was put on. The fix is to get a new gasket and put it on.

  • terry singer Aug 29, 2010

    Man You ROCK!!! My wife and I solved our '99 SL1 "racing on start, park, neutral, in-between gear changes (AT), with your advise, twocans of Berryman's Carb Cleaner and two bleeding nuckles 'cause I refused to pull the throttle body and just r

  • terry singer Aug 29, 2010

    seems most of my comments did not make the matter. We're donating $59 to The ALS Association of LA



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1 Answer

How to adjust idle speed

Remove air filter, warm up engine, plug the IAC port (the small hole in the bottom of throttle body) the adjust idle screw c/wise or anti c/wise to set rpm. REMOVE IAC plug and check the performance. Good luck.

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I have a 1999 Saturn 4 cyl. The engine idles around 1200rpm. Even during normal driving the engine still idles high even after warm up. Sometimes the engine won't start after it has sat for 15 minutes or...

leaking o-rings at the fuel injectors would explain the hard starting when warm-when you hold the petal to the floor, it shuts off the injectors, which will make it possible to start it after the injectors leak down on shutdown. O-rings are easy to replace, just disconnect the battery and pull the injectors straight up to remove, get the old rings out and install the new ones, light lubricate the base of the injectors and pop them back in.

that might explain the high idle too, although usually the idle is not consistent when the injectors are leaking at idle-idle is rough. I would make sure the engine coolant temperature sensor is new (they are very important on saturn, the original one is plastic and they are known to crack easily-the replacement should be brass)-also, check the Idle air controller, best to remove the throttle body (4 bolts) and remove the IAC and clean it thoroughly, being careful not to get the top half wet-sensitive electronics. Clean the post that the IAC goes into, and clean the throttle body (both sides) while you have it out.

Feb 21, 2011 | 1999 Saturn SL

1 Answer

99 sl1 with 1.9 has high idle and will not idle below 1200 in drive

remove the throttle body (4 bolts) and then remove the idle air control (bolted to the TB, between the firewall and the throttle body)-clean the TB, the Idle air controller and remove the Throttle Position Sensor (opposite the IAC) and clean it if necessary. The IAC carbons up on these cars, as does the Throttle body-I know, I have a 99 SL with 180,000 miles, it is almost like an oil change as they get older.

Feb 18, 2011 | 1999 Saturn SL

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Saturn 2001 SL idles in neutral between 2000 and 3000 after engine gets warmed up. also blower for heater has bad resistor were is it located so i can replace it?

high idle concern is probably caused by either a sticking throttle plate, defective IAC or the computer is commanding the high idle for another reason.

the blower motor is found behind the glove box in the HVAC case

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1999 saturn with 1.9 engine. trans does not feel like its shifting right, idle stays at about 1700 r.p.m, and i had a code for trans. electrical problem. any hep?

Can you explain the shifting problem you are experiencing? Is it a slam into reverse and/or forward gears? Is there any slipping in forward gears?

The idle may be due to a dirty Idle Air Control (IAC) valve or a faulty Throttle Position Sensor (TPS). The first step is to remove the throttle body and clean it with some carb cleaner and get the black carbon off of the IAC and the underside of the throttle plate.

What was the code for the trans? Was it is incorrect gear ratio code or a vehicle speed sensor code?

Jan 24, 2010 | 1999 Saturn SL

1 Answer

How do i know if it is my ECTS or IAC for high reving in my 98 saturn sl sohc

The engine coolant temp.sensor and idle air control will usually make the check engine light come on if they go bad.If you have high idling then check for vacuum leaks or sticky throttle.

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Idling problem

Did the "service engine" light come on in the dash near the speedometer?
There is a small electric motor located on the throttle plate called an "IAC" motor (idle air control). Its purpose is to maintain the corrrect idle speed when required such as your stop light situation. Occationally the motors "pintal" that controls the idle speed will get stuck in the bore seat and can't control the air flow of idle any more.
It may be dirty and need cleaning or the motor could be bad and gone to the great junk yard in the sky. The electrical connection and wiring should be visually inspected for corrosion or damage near the motor assembly but should not be an issue.
Let meknow what you see.

Feb 04, 2009 | 1995 Saturn Sl

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