the wires on the sensor should be in a plug and should be really easy to disconnect. It's the first sensor on the front of the intake manifold. Ther is a procedure for checking it in the 1985 FSM that is available for download here in another sticky thread near the top of the main page. It is on page FI-68 in the EFI section. There is also a procedure for removing the combination guage to get to the temp gauge in the FSM. I suggest you download it as there isn't too many serious changes from 85 to 88. It will be very applicable. I pulled my combo meter in less than 20 minutes yesterday. A Haines manual also has the info. If I can figure out how to copy a .pdf pic from the FSM and post it I will, but don't know how yet.
Here's a pic of where the sensor is on my 93 and it's in the same location on your 88, but might appear a tad different.



btw Roger that was excellent info in that link you provided - thanks <img src="/forums/images/graemlins/cheers.gif" alt="" />

Thanks for all the help and good info. I found it. Its on top of the motor next to the thermostat housing. I replaced the sending unit and now its working fine.

Don and Barb