Idle increases as it warms up Options

[Catweazle]

Hi all,

I'm new here and have recently purchased a 97 st202 2.0 3gse which I've just changed the head gasket on. I,m not sure it needed one but there were some indications there may have been the start of a leak. I was getting a lot of water (clear)from the exhaust and it was blowing what looked like white smoke,but could be the water condensating? There where also tiny bubles in the radiator, like a sea foam.
On startup after finishing the repair it all seemed fine idling around 750-800 rpm but as it warmed up the revs increased. By the time it was up to tempreture on the gauge it was idling around 1500- 1800 revs. The fan kicks in as it should and other then the high idle the engine sounds o.k. I've had a good look around and there are no obvious signs of vacuum leaks or wires off. I did also clean the throttle body when putting it back together. Any idea on what may could be causing the high revs would be appreciated.

Thanks

This post has been edited by Catweazle: Dec 22, 2014 - 1:25 PM

[antoine64]

I have a similar problem but it's just a high idle that never comes down. I have a 3sgte turbo. I'm testing the ISC valve and temperature sensor wires. I think I have either a faulty temperature sensor or bad wiring. I'll post what solves my problem in case you have the same issue.

I fixed my problem.
Here's what was wrong:

My problem might have been a bit unique. I solved it. We'll see if any of this is helpful to you.

The previous owner hooked up the power steering idle up vacuum line to the air hose from the idle control valve. he then plugged the hose choking off the idle. He compensated this by adjusting the screw under the throttle to increase the idle. This fixed his problem but made it so the engine computer couldn't control the idle. his plug leaked causing the initial high idle that I noticed. I also had some issues with the plug connectors on the air temperature intake sensor, on the throttle position sensor and on the idle control valve.

so I did these things

-fixed the vacuum hoses separating them from the air hose
-fixed the wiring on my air temperature intake sensor
-took apart the plugs on the throttle position sensor and the idle control valve and pried up the lower parts that press against the pins.
-adjusted the throttle position bolt so that the throttle was completely closed. This is probably closer to default.


so idle problems can be from

-temperature sensors for air and water.
-vacuum leaks
-over adjusting the idle screw
-a failed throttle position sensor
-a failed idle control valve
-plugged air hose for the idle control valve
-electrical connectors not making good contact with the sensors or idle valve.

Good luck


This post has been edited by antoine64: Dec 28, 2014 - 12:04 AM

[antoine64]

My problem might have been a bit unique. I solved it. We'll see if any of this is helpful to you.

The previous owner hooked up the power steering idle up vacuum line to the air hose from the idle control valve. he then plugged the hose choking off the idle. He compensated this by adjusting the screw under the throttle to increase the idle. This fixed his problem but made it so the engine computer couldn't control the idle. his plug leaked causing the initial high idle that I noticed. I also had some issues with the plug connectors on the air temperature intake sensor, on the throttle position sensor and on the idle control valve.

so I did these things

-fixed the vacuum hoses separating them from the air hose
-fixed the wiring on my air temperature intake sensor
-took apart the plugs on the throttle position sensor and the idle control valve and pried up the lower parts that press against the pins.
-adjusted the throttle position bolt so that the throttle was completely closed. This is probably closer to default.


so idle problems can be from

-temperature sensors for air and water.
-vacuum leaks
-over adjusting the idle screw
-a failed throttle position sensor
-a failed idle control valve
-plugged air hose for the idle control valve
-electrical connectors not making good contact with the sensors or idle valve.

Good luck

[Catweazle]

Hi again,
I eventually got to the bottom of this.
The Idle Speed control Valve (ISC) was stuck wide open. This meant that the engine was getting a maximum amount of air entering the engine and therefore the ecu was incresing the amount of fuel causing the idle to be high. Cleaned the valve, which then closed to its proper position and the idle now settles down to around 750rpm once warm. I think this fault may have contrbuted to the amount of water coming out of the exhaust which has now also decreased.

Thanks for your contributions