I heard a question a couple of weeks ago about a car that was functioning at low idle speeds because a sensor was malfunctioning on reading the engine temperature. Does anyone remember this question or the repair suggested for this problem?
I don’t know where you heard this. I remember one about low gas mileage and the suggestion was one of the temperature sensors. There can be up to three of them.
As for low idle speeds, that can be caused by either the computer is not getting the signal that the driver has taken his/her foot off the gas or the IAC (idle air control) is not working. I’d bet on the foot off the gas signal, sometimes called the IPS (idle position sensor) if it is a separate sensor or the TPS (throttle position sensor).
The most common problem is that the throttle plate does not completely close, usually due to a dirty throttle body, so the TPS does not go to zero position or the contacts are not made in the IPS. The the computer does not know it is supposed to take over the idle speed via the IAC. A simple throttle body cleaning should do the trick.
Does this T-bird have a tachometer?
Often the terms “low idle” and “rough idle” are used interchangably-- is the engine idling below the specified RPM’s (which you can find on the emissions sticker under the hood), or is it at the correct engine speed but is loping and bumping around?
If the former, look at the IAC, TPS and CTS. If you have a service manual and an Volt-Ohm meter you can test these components. If the latter, a general tune-up is in order.