'93 XL, 3.0. This rig is amazing. At 230K, it still has great oil
pressure, plenty of power and does everything asked of it. I had it
into the shop to replace the ignition switch, the idiot oil pressure
sensor, which reads much lower than reality, and the headlight
switch. When I got it back, the speedometer, which was always smooth
and accurate before, started acting erratically. Huh? It would
"bounce" just a tiny bit at 30 MPH+. At 50-70 MPH, the needle bounces
wildly back and forth (+/- 20 MPH), only occasionally hesitating...
just long enough to have some idea how fast I'm going. I could ignore
that and go with the flow, but it also rendered the cruise useless,
which really sucks. I just drove a 1400 mile trip using my now, very
tired right foot on the pedal.
Being old school, first thought was that the mechanic somehow crimped
the speedo cable, while behind the dash. But alas, I found that this
rig doesn't have a speedo cable. The now-off-the-hook mechanic
suggests that it's either the speed sensor, or the dash unit itself.
Before I start randomly replacing pieces, I'm sure some of you have
experienced this and can venture an educated guess.