fiancee's dad's car... it's a 4banger with a stick.

Sometimes the tach reads a little low, sometimes it reads high.

It doesn't go up to 4k rpm or anything crazy when he's cruising around, he says it reads about 1750rpm at idle sometimes and on the highway it'll read 1500rpm.

I'm not sure if there's some magnetic sensor near the flywheel that the tach runs off or if the tach is run old school off the distributor or if it's a cluster issue. Any help would be appreciated.
-Matt

 

nobody knows what could be causing this issue, or even how the tach works (which may help in finding the issue)?

 

your cluster might be screwed up.

 

its called the VSS(vehicle speed sensor) but it would throw a CEL and the speedo would also be screwing up

 

that would be if the speedometer is reading wrong, right? This is the tach, aka "rpm meter".

 

The tachometer gets its signal from the distributor. Mine was acting funny(bouncing) and it was an early sign that its was dying. Once it got hot it would buck a little and the engine would die.
I bought a new one a advanced with a lifetime warranty.

 

His car has trouble starting when ambient temps are warm. When it's cooler or cold, it fires right up! I know the factory intake is basically junk, but could it be due it wanting to run rich (mpgs are lower than they used to be also, he says), and being colder the engine gets more oxygen (and the fuel mix is more stoichometric) so it starts/runs better?

Seems to me that could be a intake air sensor issue with his engine. But back to the tach, the dizzy seems to be a legitimate culprit as it is well past 200k miles, 250k will have passed under that car before too long! (this is on regular oil too! but it sees mostly highway miles, with some city at each end of the ~1hr commute)