Check engine light on

["Block, Paul" <Paul.Block@fortjamesmail.com>]

Sorry to be asking, as I'm sure the answer to this is in the archives, but I
currently don't have access to www.  
The check engine light on my 88 5ksq just started lighting up.  It doesn't
matter if the car is hot or cold, as soon as car reaches 2000 rpm the light
comes on and then stays on, until I turn off the key and restart. The car
still seems to run ok, but I have not been driving it much since the light
started coming on (switched to my 'trusty rusty 4kcsq'). I have been unable
to locate any vacuum leaks, broken wires or other obvious causes.
Previously, the light never came on, with the exception of when I first
turned on the ignition, and all warning lights light up for a few moments.

Please respond to me at paul.block@fortjamesmail.com
<mailto:paul.block@fortjamesmail.com>  as I am not currently subscribed to
the list.
Any help solving this one is greatly appreciated.
Thanks in advance.
-Paul Block