1g Talon Idles Rough after it's warm!

[540eclipsers97]

I have a 1992 Eagle Talon TSI. It has started to idle really rough after it gets to operating temperature. When it's cold it idles normally. Also the haed was just rebuilt 800 miles ago. I just bought it 1 week ago and it's done this since I bought it. It puts out 11.0 psi so I don't think i have any boost leaks and it has no problem gettin to up to speed. Also, the valve cover is leaking from all sides. Could that be the problem? any help would be appreciated.

 

[gofer]

The VC leaking is a problem whether your cars idling like crap or not, when you get up to speed and the oil pressure increases it fills the head with oil. If its leaking bad your losing lots of oil just driving down the interstate because of a $40 gasket, you should get that fixed ASAP.
Try making adjustments to the BISS (plastic screw in your throttle body) while the cars idling its free and an easy way to see if it just needs adjusting. Screwing it in further will lower your idle speed and screwing it out will raise it, play with it a bit and see if it fixes the problem. If not do the below tests to see if its a sensor...


The first thing you should test is your CTS (coolant temp sensor) using a multimeter. There are (3) sensors in your thermostat housing...

-The A/C temp sensor which is in the upper half of the t-stat housing.
-The GAUGE coolant temp sensor gauge, its a single wire tapped sensor.
-The ECU coolant temp sensor thats in the lowest part of the t-stat housing, it angles downward a bit too.​

You'll want to test the ECU coolant temp sensor but to do it correctly you'll want to start the test with your car COLD and using a DMM check the resistance at the back of the sensor.

Below is a chart of what resistance reading you should get if the sensor is working correctly according to the temp. of the coolant.

• 32*F = 5.9k ohms
• 68*F = 3.5k ohms
• 104*F = 2.7k ohms
• 176*F = 0.3k ohms

Heres a picture of the sensor locations if the description above just confused you.

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If its not the CTS then its possible your o2 sensor has failed and not throwing a CEL. You can check the sensors heating coil for resistance but if it tests good that doesn't necessarily mean the sensor isn't bad. The only way you can check it for sure is by watching the voltage on a logger or replacing it. To test the heating coil measure resistance between pins 3 & 4 using a DMM, it should measure 12 ohms at 68*F. Heres a picture of the o2 sensor harness and the pinout so you know what pins to measure resistance at.

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Post your results and let me know what you find.

 

[540eclipsers97]

It has a non turbo radiator on it and has no thermostat. It was like that when I bought the car. It stays at normal temp. Though.

 

[gofer]

It has a non turbo radiator on it and has no thermostat. It was like that when I bought the car. It stays at normal temp. Though.

I don't know what that has to do with testing the coolant temperature sensor to make sure its working? Running the N/T t-stat housing just means you don't have coolant lines running to your turbo so I hope you've got a turbo timer on that car.
Now that I know your not running at thermostat at all you might just need to put a t-stat in there, if the coolant never reaches 190*F or more then the ECU never goes into learn mode which means it will idle like crap after its warmed up because it never updates idle fuel trims.

Just because your gauge shows that your coolant temp is good that doesn't mean the ECU is seeing the correct coolant temperature, there are THREE sensors that read the coolant temp. The ECU ONLY watches the ECU's coolant temp sensor NOT the sensor to the gauge, and from the temp of the coolant it operates in open loop or closed loop. If the CTS fails and shows a temperature below 87*F to the ECU it will idle as you describe too.

Adjust the BISS on the throttle body, check the CTS, and then test/replace the front o2 sensor.