What sensors and/or modules should I look at for a tachometer problem?

It's possible that the 2004 Ford Ranger's engine or the tachometer itself is to blame for the difficulty you're describing with the tachometer reading. A crankshaft position sensor issue is one typical reason for a tachometer to read high. To determine the engine's RPM, this sensor transmits signals to the engine control module (ECM). The tachometer may show a reading higher than the real RPM if the sensor is broken.
There are several possible causes for this issue, including a problem with the tachometer itself, a problem with the sensor that sends information to the tachometer, or a problem with the vehicle's electrical system. It is also possible that the tachometer cable is loose, damaged, or disconnected.
It's recommendable to take your truck to a professional mechanic to diagnose and fix the problem. In some cases, the problem might be fixable by replacing the sensor or cable, but in other cases, it may require more extensive repairs or replacement of the tachometer itself.
It's also important to note that even though the tachometer is not working properly, it does not affect the performance of the engine, but it will give you a wrong idea of the RPM, which could lead you to over-rev the engine and cause damage.

this could be the tach meter itself. there is no bad consequence to driving it this way just annoying.

4cyl or 6 cyl?

I am not a Honda guy but that sounds like fuel flow blockage to me. Try filter, then lines. Maybe clean the airflow sensor are too.

If you have no other symptoms other than a faulty reading then it can be 2 things, leaking ignition high voltage wires or a faulty tach, i would go with the tach.

Then you have a intermittent spark . Now do you have a spark tester to test spark. Its okay if you dont we have one . Oh by the way you did the fuel pump yourself. if you can do a fuel pump then you can do this to solve the no start problem. No spark tester? okay we will use that tachometer (RPM gauge). crank the engine does the tach meter reads zero at all times while cranking, if it does youll need a crank sensor. Here the story Rough running conditions and or stalling was caused by a faulty crank sensor, try shaking the connector or wiggle the crank connector then see if it starts. Youll need to inspect the connection for proper male to female connection these have been the most suspectable failure of KIA. If you decide to replace this sensor make sure connections are good, more than likely this was the problem and not the fuel pump

The coolant temp sensor is shot. Replace it. When it is connected, it gives the ignition module erroneous temp readings, and computer reacts randomly.When sensor is disconnected the car behaves as if it was cold, and it runs steadily, but probably not burning efficiently, and more important, module detects the missing sensor, and turns on the check engine light.

Do you have engine code showing by chance? It's possible the crank sensor is bad or the connection to the ecm or pcm to the instrument cluster circuit board needs a look. If you need schematics check out www.promanuals.net they specialize in Dodge Ram service manuals.

Do the following:1)key in the ON position:remove the 7.5 gauge fuse.Tach needle should read "0:". 2)put it back,go on the engine and unplug the green plug on the igniter -the big one,with 5 or 6 wires on it.The needle on tach reading should be zero.If not you have a short circuit on the black wire between that plug and the plug on the conbination meter.3) If the reading is zero with the plug disconnected,the black wire for the tach is short-circuited inside the igniter. I have one available.email [email protected]

You will need to remove the tach and have it repaired by a factory authorized service center, don't go through the dealer, they will 2X the price.