My tachometer has started acting funny in the last few days. I will be driving along, and it will suddenly indicate ~800-1200 RPM more than then engine is doing. There is no change in the actual engine speed.

Sometimes, it's a quick blip, and sometimes it continues to read wrong for a while.

Any ideas why it would be doing this, and what can be done to fix it?
The truck is a 93 with the 5.8L, and 168K miles. I was planning on replacing the coil with an MSD so I can increase the gap on my plugs. Would doing this possibly fix the problem?


Thanks!!

 

If the tach, itself, isn't going bad (and assuming the associated wiring is okay), I'd keep a very close eye on your ignition system. Many times, ignition components going bad can show up in bouncing / erratic tach readings. I've seen this, myself, in: bad spark plug wires, bad stator/coil, bad ignition module, and in a distributor with shot bushings. With 168K miles, you may check for bad connections and then consider what components may be due for replacement, anyway (cap, rotor, wires?). Just a couple of thoughts.