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Shawn
Shawn, ASE Certified Technician
Category: Car
Satisfied Customers: 655
Experience:  PA Certified Inspection emissions, ASE Brakes Suspension, Lead diagnostic Tech.20 years exp
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My 1999 Saturn SL is idleing too high (3000 RPM)

Customer Question

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Submitted: 8 years ago.
Category: Car
Expert:  Shawn replied 8 years ago.

whitey,

Your high idle is most likely a vacuum leak. I've had a few with leaking intake gaskets around number one cylinder. Check all vacuum lines for splits or breaks. You can spray some carb cleaner around the throttle body to manifold mating surface and the intake manifold to head and listen for the rpms of the engine to change. Be careful around the exhaust manifold when you are using the cleaner. The electric items on the throttle body are the IAC valve and the throttle position sensor. The IAC valve can create idle problems but not usually this high. 3000rpm is a good sign of vacuum leaking.

 

Let me know if you need anything else.

 

 

 

Shawn

Customer: replied 8 years ago.
Thanks for your reply Shawn. The reason that I think it is an electrical issue is because if I shut the ignition off and on while its high idling, the idle will fall to normal 900 rpm. Then I drive it, at next stop sign, the idle is again up at 3000 rpm. Sometimes while parked in neutral, the idle will fall all by itself back to nornmal..then for no reason climb back up to 3000 rpm. Very strange. I had a mechanic check it out and he cleaned the throttle housing and checked for vacuum leaks, but could not find any.
Expert:  Shawn replied 8 years ago.

Ok. That does change things. Stay on, I'll will be right with you.

Do you have access to a scan tool that can read datastream from the PCM?

 

 

Shawn

Expert:  Shawn replied 8 years ago.

Whitey,

Idle is PCM controlled by various sensor inputs. Saturn had a problem with coolant temp sensors that where cracking , leaking and /or had corroded terminals. Unplug your coolant temp sensor and check the terminals for corrosion , check for wetness inside and look at the plug for corrosion. If any wetness or corrosion is found, replace the coolant temp sensor.

The other area to check requires a scan tool to allow you to adjust idle manually through the IAC to determine if the IAC is working properly. Coolant temp sensor can be checked to see if it is reading properly with the scan tool.

Have you had a check engine light and if so, what were the codes? This will help further for either you to fix or if needed, have your tech fix.

Get back to me with the engine and model and we can get further into what to check. SL1/SL2.

In the end. If it's not vacuum which from your description, it isn't. It lies between the IAC or temp sensor. Temp sensor will create erritic idle.

The more information you can give me, the quicker we can get an answer.Meawhile, try checking that temp senor as described. It is on the trans side of the engine.

 

 

 

 

Shawn

 

 

Customer: replied 8 years ago.
It is a SL1 coupe.

I will check the coolant sensor you mentioned. The mechanic I had look at the car out itthrough the scan and no codes came up and tere is no "check engine" lights on.

I will check the sensor and get back with you.

Thanks.
Expert:  Shawn replied 8 years ago.

Ok whitey. I'll watch for your response.

 

 

 

Shawn

Customer: replied 8 years ago.
Is the sensor on the engine block or the radiator?
Expert:  Shawn replied 8 years ago.
Engine.
Customer: replied 8 years ago.
Thanks Shawn
Expert:  Shawn replied 8 years ago.
You are quite welcome sir.
Customer: replied 8 years ago.
Shawn,
I cant seem to locate the coolant sensor on the block thst you spoke of. Could you please provide a more detailed description of where it is located and what it looks like? Does it look like most temp sensors? Like a spark plug almost?
Expert:  Shawn replied 8 years ago.

Whitey,

It's on the rear of the cylinder head right below the thermostat housing.

Here is a better pic of component locations. It's for a 2000 but is the same as 99. 2000 just has a better reference picture for some reason.

 

Shawn

Expert:  Shawn replied 8 years ago.

Sorry. Forgot to add pic.

 

 

 

Here you go

Customer: replied 8 years ago.
Thanks, XXXXX XXXXX it out.
Expert:  Shawn replied 8 years ago.
Ok. Let me know how things work out.