2001 xterra vehcile speed sensor problem

HOW HIGH IS TOO HIGH RPM? (NO TACHOMETER?)
NO ENGINE TOLD OF MANY SO ANSWERS NOW GO GENERIC.
ALL ENGINES CARS, FAST IDLE LOCK IS BASED ON ECT SENSOR COOLANT TEMPS, AND COLDER IT IS THE FASTER IT GOES.
EVEN BY EPA LAW USA.
cold is 1500 to 2500 most cars. pcm logic hard facts. and tables.
fluctuates is super bad and dangerous A.K.A SURGE.
there is no pat answer to this, so many engines.
but here are some.

• IAC BAD. (IDLEAIR CONTROLEER VALVE) THERMAL
• ISC STUCK (IDLE SPEED CONTORLLER ELECTRIC.
• THERMOSTAT BAD, OR MISSING.
• ECT READS WRONG/ Most times see 1 line up.
• VACUUM LEAKS FROM VAST THINGS. (YES VAST)
• PCM IN LIMPHOME MODE NOT SCANNED AND IDLE CONTROLS 100% OFF LINE. AND SURGING.
• GROSS MISFIRING.
• GROSS LEAN BURN AND SURGE.
• other sensors failing hard and you not scanning PCM miss the boat.

.

It's probably in limp home mode. Check RPM dial most likely wont go past 2500-3000 RPM in any gear. This is for safety when the ECU find's almost any fault it will cut the engine to save damage. Get the ECU checked for fault's fix reset and it should run properly

MAP sensor may be going bad letting it over fuel the engine causing black smoke and bogging RPMs .

Check the transmission fluid level. May be low and getting too hot.

Is your check engine light on?

If you take it to Autozone to have a free check they will tell you its the mass air flow sensor. So you put it on and it still has the same problem except now your out of $125. If your check engine light is on too then take it to a place where they can check out the codes and tell you exactly what you need. About $80 for the check. You can't guess at these things and AZ only tells you what might be wrong. Good luck

From the service manual:

Idle Speed/Ignition Timing/Idle Mixture Ratio Adjustment
NGEC0549
PREPARATION
NGEC0549S01
1) Make sure that the following parts are in good order.
I Battery
I Ignition system
I Engine oil and coolant levels
I Fuses
I ECM harness connector
I Vacuum hoses
I Air intake system
(Oil filler cap, oil level gauge, etc.)
I Fuel pressure
I Engine compression
I EGR valve operation (If so equipped)
I Throttle valve
I Evaporative emission system
2) On air conditioner equipped models, checks should be carried out while the air conditioner is OFF.
3) On automatic transmission equipped models, when checking idle rpm, ignition timing and mixture ratio,
checks should be carried out while shift lever is in “N” position.
4) When measuring “CO” percentage, insert probe more than 40 cm (15.7 in) into tail pipe.
5) Turn off headlamps, heater blower, rear defogger.
6) Keep front wheels pointed straight ahead.
7) Make the check after the cooling fan has stopped.

SEF976U
3. Open engine hood and run engine at about 2,000 rpm for about 2 minutes under no-load.
SEF977U
4. Perform diagnostic test mode II (Self-diagnostic results). Refer to EC-644.
SEF217U
OK or NG
OK ' GO TO 2.
NG ' 1. Repair or replace components as necessary.
2. GO TO 2.
BASIC SERVICE PROCEDURE VG33E
Idle Speed/Ignition Timing/Idle Mixture Ratio Adjustment (Cont’d)
EC-616
2 CHECK IGNITION TIMING
1. Run engine at about 2,000 rpm for about 2 minutes under no-load.
2. Rev engine (2,000 to 3,000 rpm) two or three times under no-load, then run engine at idle speed.
SEF978U
3. Turn off engine and disconnect throttle position sensor harness connector.
SEF975R
4. Start and rev engine (2,000 - 3,000 rpm) two or three times under no-load, then run at idle speed.
5. Check ignition timing with a timing light.
SEF371S
15°±2° BTDC (in “P” or “N” position)
OK or NG
OK ' GO TO 4.
NG ' GO TO 3.
GI
MA
EM
LC
FE
CL
MT
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
BASIC SERVICE PROCEDURE VG33E
Idle Speed/Ignition Timing/Idle Mixture Ratio Adjustment (Cont’d)
EC-617
3 ADJUST IGNITION TIMING
1. Adjust ignition timing by turning distributor after loosening securing bolts.
2. Turn off engine and connect throttle position sensor harness connector to throttle position sensor.
SEF972R
' GO TO 2.
4 CHECK BASE IDLE SPEED
With CONSULT-II
1. Read idle speed in “DATA MONITOR” mode with CONSULT-II.
PEF356V
700±50 rpm (in “P” or “N” position)
Without CONSULT-II
1. Check idle speed.
700±50 rpm (in “P” or “N” position)
OK or NG
OK ' GO TO 6.
NG ' GO TO 5.

probably the vehcile speed sensor

I have a 2002 Dodge Ram that doesn't like to shift into 2nd when flooring it from a Stop. Imagine if you were to floor the gas in neutral, the engine REDLINEs and the engine governor kicks in to keep the RPM from blowing the engine......while stuck in first Gear. If i let off the gas, it goes into 2nd fine. I have replaced the Speed Sensor on the transmission ($18) and it seemed to fix it for one day. After 200 miles, its doing it again. ANybody have legitimate answers in here? Its only got 60K miles..wtf?