Thanks for the tip Phillip. Auto Zone lends out readers for no charge (refundandable deposit required). I plugged it in and found out that my engine coolant temperature circuit is faulty.
I have a Chilton's service manual and tried to find the coolant sensor but to no avail. It is supposed to be on the intake manifold, but I couldn't see anything that looked like a two terminal sensor screwed into the manifold (viewing from the top side), which is where the manual indicated it would be. Of course, the manifold is surrounded by dense tubing, which makes inspection more difficult. Do you have any idea where the temp sensor is located?
Thanks,
Mark