My truck is missing out and it seems to be very noticeable in 2nd and 3rd gear. in seems to run fine at idle but under a load u can notice the miss. i have a 2000 ford explore sport 2 wheel drive 5 speed manual trans.

NISSAN , not the same at all, ARE different. ABS, idle and trans.
p07xx is transmission errors and told here by SM
505 IS IAC IDLE VALVE STUCK ERROR OR VACUUM LEAks
no IDLE RPM TOLD HOT. MATTERS HUGE.
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744 TCC IS THE TC LOCKUP SOLENOID WIRE FROM PCM TO TC.
THE TCM(PCM) SEES IT FAIL 2 WAYS.
DEAD, rpm OF TRANS (vss) FAILS TO DROP IN HI GEAR.
OR IS CAUSING LOW VSS READING STUCK ON.
744

• Low transmission fluid level
• Dirty transmission fluid
• Faulty Torque Converter Clutch (TCC) Solenoid Valve
• Torque Converter Clutch Solenoid Valve harness is open or shorted
• Torque Converter Clutch Solenoid Valve circuit poor electrical connection

ABS LAST IF BRAKES SEEM OK,
ABS CAN FAIL OF LOTS OF REASONS, AND YOU HAVE NO ABS SCAN TOOL AT ALL I BET.
GET THE ABS SCANNED FULLY THEN FIX IT. <<< do it now.

then you say 3rg gear is missing
well, did it jump 2 to 4th gear
or is 3rd gear FLARE, a false neutral.
the transmission needs to be fully checked out. for sure tranny line pressure (pump) ports in all PNDRL selections as the SM told you.
service manual,

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You must have an engine misfire, one or more cylinders is missing and has no power output, this is most noticed under a load, not at idle in park. You need to have the computer tested for fault codes, any Autozone can do this test for free. .

Year/make/model??? Not going to be a timing belt issue. Possible ignition problem. Spark plug/wire/ignition coil

It sounds like you have a misfire. Does it miss more under a load or does it miss primarily,at idle. If under load, it is likely ignition related. Spray water on the wires and coils with the engine running. If they are carbon tracking it will be very obvious as the engine will miss worse.

The fact it only has a possible misfire in the first 3 gears,
tells you your under a high vacuum load getting up to speed
& applying more gas pedal command as well, until you let up
in top gear

Timing is engine load related, so your theory is not valid there either

I would do a cylinder leak down test to check the mechanical condition
of the motor,valves & such,then use an evap smoke machine to test
intake,exhaust & evap system for vacuum leaks

What about EGR System Even electronic ones use vacuum,thus
my vacuum load theory.

Get rid of all ignition misfire issues

No Vacuum Leaks anywhere on car

New upstream O2 Sensors or scope yours for
switching times

Check timing belt for issues

I guess you checked fuel pressure

Check alternator for bad diodes

Need a scan tool to look at fuel trim & all data
on a road test

Basically you missed something

You notice the miss when going up a hill because you are putting the motor under load, sounds like time for tune-up, pretty sure the miss is there all time, but you just notice it more when under load

Check both O2 sensor(s) and catalytic coverter.. P0420 means catalyst below threshold. Also check the sensor at the transmission and solenoid.

My timing was off in mine. Check the timing gear, its a ***** to replace but it will be worth it or if you mess with the destributor cap turning it a couple teeth that will work too. I did this to mine and the rough idle went down and i don't have a miss anymore. Just make sure you know what you doing or you could make it worse.

just ram the shifter in your booty,.....duh