Try running a self test on the EEC-IV system (better known as scanning). Transmission codes do not light the "check engine" light in that vintage.
IF your transmission is electronically controlled, a speed sensor is a definite possibility.
IF your transmission is NOT electronically controlled, the problem could be a vacuum modulator, governor, or valve body problem.
To determine which transmission controls you have, look at the transmission where the manual shift linkage enters the case. If there is a large switch there with a multi-wire connector, it is electronic.
If not, it will have a vacuum modulator on the right side of the case near the catalytic converter.
Let me know which one you have, and I can advise you further.
SPONSORED LINKS
Thursday, January 8th, 2009 AT 2:08 PM