What would make my TBI motor run fine when it is cold, but when it gets hot, it runs bad?

 

It could be several things. below a certain temp. the computer does not do any correction to the fuel, it runs off of pre-set tables. I would check your o2 sensor, to start with.

 

Thanks, I was thinking that there was some kind of coolant temp sensor, that controlled something , could it be that?

 

There are things that the coolent temp sensor controls, but if the temp sensor is not working, it should have problems all the time. The fact that it works until i get hots, makes me think the temp sensor is working. If you have access to a scan tool, you can easily check the output of both the o2 sensor, and coolent temp sensor.

 

Theres a possibility that the CTS is faulty. If there is an excess of resistance, it can cause teh computer to register the coolant temp as being less then what it actually is. Itll cause the motor to run excessivly rich.

 

In case your wondering, the CTS is a sensor mounted on your manifold next to the thermostat housing.