Are there any tips/tricks to replacing the coolant temp sensor and the cold start switch? Where are they located? I have an 87 GT with some idle problems (which, judging by the quantity of threads, seems to be very common) so I am going to begin to replace things until I nail it down.

quote Originally posted by jwbfiero: Are there any tips/tricks to replacing the coolant temp sensor and the cold start switch? Where are they located? I have an 87 GT with some idle problems (which, judging by the quantity of threads, seems to be very common) so I am going to begin to replace things until I nail it down.

The coolant temp switch is below the thermostat housing and goes into the lower manifold horizontally. The CSS is to the right of the thermostat housing, has an injector type connector. Next to it is the fan switch which has one connector. The CSS can be removed and inserted without any coolant loss, the coolant sensor, however may leak some coolant, so you may want to siphon some out through the thermostat housing. I do not think the CSS would cause a bad idle,( poor starting), but it is only on during cranking............Paul

[This message has been edited by Paul Prince (edited 08-02-2004).]

Does your check engine light come on? Usually it will, if there is a problem with sensors. If so then you should pull some codes from the computer to see what the problem is. The "replacing things untill you nail it" can get expensive.

The cold start injection system consists of few parts, none of which are connected to the ECM. The power for the CSI comes from the starter solenoid, so it only sees power when you're cranking. As soon as you stop cranking because the engine starts or whatever, the injector loses power and stops spraying fuel. In any case, the CSI thermal switch is a timed switch that will run for no more than 8 seconds on below zero days and doesn't even work at all when the coolant temperature is above 90°F. Normally the CSI isn't known for failing since it is rarely on. If it fails typically it's as a leak, the car runs rich all the time.

JazzMan

My check engine light does not come on. My symptoms, which seem fairly common to the forum, are hunting idle at cold start up, hesitation at cold start up, and slight popping/surging at first application of the gas pedal at cold start. If I put the pedal to the floor it seems to "blow itself out" and the problem goes away. But it is a very consistent problem....every morning. Any thoughts?