Tachometer not working on 96 cougar. Goes to 2500 rpm on start up and sticks

Question edited for clarity and typo.
Question moved to model category.

It is a known issue. Lots of information in the link and also a video.

https://www.google.com/search?q=1990+Ford+F-150%2C+Tachometer+sticks

Tachometer / Speedometer Problems: - Ford Explorer and Ranger ...

www.explorerforum.com > ... > Under the Hood

Jul 31, 2006 - 13 posts - ‎11 authors
Tachometer / Speedometer Problems: Under the Hood. ... upon restat the speedo goesto (is driven to) zero, the tach goes to ... 88 89 93 95 96 Aerostars ... in cold weather it seems to stick. but once the truck's interior warms up, .... 1995 Ford Explorer 4.0Automatic My Tach Quit Working And So Did My ... 5R55S harsh shifting; bump engaging reverse;
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1999 Ford Explorer , Erratic RPM Problem - YouTube

A/T tranny"drive"
are the brakes iced over.?? i can't know this. only you.

if not, ice, then tranny is sick
get help

do you have a dash tachometer? RPM?
this instrument tells you what is wrong,
1: Tacho RPM buzzes high bad tranny.
2: tacho rpm sticks at say 2000rpm not running free with right foot action that means the breaks are locked up with ice or hand brake is ON.

Ignition or fuel problem probably . When you turn the key to start does the engine spin ? Crank no start or nothing happens NO CRANK - NO START ?
If the engine spins an does not start an run you need to test to see what's missing Spark or fuel . Pull a spark plug wire off a spark plug an stick a screw driver in the end an hold it near ground (metal) and have someone try to start the vehicle ! Is there spark ? Spray starting fluid into the engine , does it start then ?
Videos on youtube showing how to do these tests

i have a 90 chevy 2500 2wd 350ci.when i go to start my truck the key turns hard in the ignition,the check engine light and brake light come on the heater dont work,and the transmission will shift from 1-2 at real high rpm and shift hard,no 3-od.this comes and goes,but all happens at the same time.some times it last for 10 min,sometimes its days.what is going on?

Look for the oil pressure sending unit on the block or the cylinder head on the V-6 or V-8 models. --- OIL PRESSURE TEST Check for proper oil pressure at the sending unit passage with an externally mounted mechanical oil pressure gauge (as opposed to relying on a factory installed dash-mounted gauge). A tachometer may also be needed, as some specifications may require running the engine at a specific rpm.

1. With the engine cold, locate and remove the oil pressure sending unit.
2. Following the manufacturer's instructions, connect a mechanical oil pressure gauge and, if necessary, a tachometer to the engine.
3. Start the engine and allow it to idle.
4. Check the oil pressure reading when cold and record the number. You may need to run the engine at a specified rpm, so check the specifications.
5. Run the engine until normal operating temperature is reached (upper radiator hose will feel warm).
6. Check the oil pressure reading again with the engine hot and record the number. Turn the engine OFF.
7. Compare your hot oil pressure reading to specification. If the reading is low, check the cold pressure reading against the chart. If the cold pressure is well above the specification, and the hot reading was lower than the specification, you may have the wrong viscosity oil in the engine. Change the oil, making sure to use the proper grade and quantity, then repeat the test. Low oil pressure readings could be attributed to internal component wear, pump related problems, a low oil level, or oil viscosity that is too low. High oil pressure readings could be caused by an overfilled crankcase, too high of an oil viscosity or a faulty pressure relief valve.
   

If the alternater output drops when the rpm's increase
you may have a slipping belt. Stop at a parts store
autozone/napa/ or advance. They will put meter on it
for free. Hope this helps.

check pcv valve for failure/sticking

Did they check it with engine at or above the 2500 rpm's?

throddle postion senor maybe