Why does the tachometer work intermitently ?

no engine stated. ouch....
all else work? car drives, no mifire????
no low MPG?
no CEL lamp glowing driving,?????? check engine light,.??
if the cluster TACH (stock ) is dead.
then its bad, or the wires from it to the PCm. are bad.
of other cluster gauges or lamps are dead, the fuse blew to the cluster.
that is all i can do working blind, id have to see all to tell all.

ill get your custer drawings and look for you, you can too at Mitchells DIY'
there is 2001 rodeo and rodeo sports. ill guess non sport.

ok the PCM if you scan it and RPM reads ok then all that is ok
the PCM on this car sends RPM data , on 1 wire to the techo,
if it arrives there, (wires) then the tacho works if and only if it has power, if the coolant gage works that means tacho has power too. as they sit on the same power rail in the head.

tachos get their signal from the coil or the ignition control module or ECM
check for ;loose / broken wires in the harness or at connections
There will be no fault codes for tachs unless it affects an adjacent sensor
could be a faulty tacho unit (tacho--tachometer--rev gauge --rpm indicator )

check for a faulty wire/s to the tacho of a faulty tacho unit
the tacho gets its reading by the ignition impulses so any engine running problems may have been a result of the faulty tacho or wires.

you have an in cluster factory engine tachometer (RPM)?
the tacho is meter in the cluster and does not use speedo parts or its cable.
its just a meter that needs power, ground and spark tacho signals
if all 3 are good, the meter is bad. period.
the tacho signal goes to the ignition coil minus lug, and will good, as engine runs. so... wires bad, to tacho or tacho bad.
ever price a new one? or even used? $100 used?
you willing to pay that much for just a factory tacho?

there is NO speedo cable. this old 93 is electronic, (rare on most 93 cars made, toy is advanced)
here is the proof, amazing how books dont lie....
there is a speed sensor.
the tacho and speedo use the same power and ground
leaving just one wire,r-g red-green RPM sig. pin 5 of cluster
an is SPARK primary sig. so if only tacho is dead.
then the tacho is bad, or that pin 5 wire is dead.
got you to just 2 possibles.

I suggest an Auto Electrician....... but you CAN do this.... BASICALLY it is a wire running from the Power Scource.... Ignition Switch,.... to the Tacho, then from Tacho to Distributor if it is a Petrol Vehicle, but a DIESEL is completely different..... THAT needs a Vacuum operated Tacho via the Injector Pump and I STRONGLY Recommend a Electrician for that..... Pain in the *** to fit to a Diesel.... I HAVE A diesel.....

ok what engine?
2.5L , 4.0L ? 4.2L
the tacho works by spark, signals and this varies by engine type.
1990 has the very odd, French REnix ECU (bendix-renix)
with no scan tool suport ,until 1993.
so scanning it for tacho signal good, is impossible. (DIY)
i sold min long ago. at 250k miles. now have 5 th jeep, 2008, a retired tech.
sold it with those rare books too. all 3 sets.
back then the engine has a small blue book, separate from main FSM.
ebay has them if patient, id recommend owning the FSM on any car
you do the work on. why work blind?>

alldata.com may have these facts.

too bad you didnt post engine. really, so ill will wild guess its a
4.2L
and answer for that.
the ignition model sense the spark signal to the Tacho
the tach is 3 pin meter. power, ground and signal.
if the signal is good and 12vdc across, power and ground pins
the tacho is bad.
if power and ground are bad fix that first.
if the signal is dead, the wire is cut or grounding out or the ignition wire
green is dead.and bad module,
on the 4.2L the green wire. goes dead kills the coil dead..

since it runs ok
that leaves way.
bad power to tacho, bad tacho.
easy peasy. this car.
other engine can work differently, (not stated)

first check if the tacho is electronic. if its manual ie uses a cable, then test and replace the cable. if its electronic, could be fuse , loose wiring, pick up on gearbox, dash problem. have to test each one individually.

The tach has failed, replace it with a used one if you can locate the part which i doubt.

if its a monsta tacho red wire to ignition in fuse panel black to earth in engine bay green to negative wire on coil if you have ecm there will be a tacho wire on points cover check that it dosent have power and that should be the one

Click on the link below to learn how to wire a tachometer to your 1998 Daewoo Lanos

http://www.ehow.com/how_4830244_wire-a-tachometer.html