Can I by pass the egr on my xterra it does not have the connection on the upper part of the motor

P0300 is a code that indicates the engine has a random cylinder misfire. The causes of this are so numerous as to not to be able to provide any real help without hands on testing. You also may need the engine control computer flashed, many vehicle makes did updates because this code keep setting and no problem was found to justify it.

first check fuse.....
then wires leading to the electro motor.....
if that is OK.... take out motor and try to connect it directly to some 12V source..... if it turns... should be OK....
if it doesn't turn when connected to wiper rods, then there can be some obstacle, or motor brushes needs to be exchanged

Bad idler sensor possibly or abs sensor

Here's a link,it tells you where it;s at,but now you know what it look's like and can see it easy. Duralast EGR Valve EGR4170 2000 Nissan Datsun Xterra 2WD 4 Cylinders 2...

EGR is for NOX

Too Rich a fuel mix is HI CO

Are the front or upstream oxygen sensors over
100,000 miles?
Air Filter new?
Always change oil before inspection & use full synthetic
Spark plugs over 2 or 3 years,won't pass insp
Clean MAF Sensor

Sounds more like the EGR valve is faulty. Change this Exhaust Recirculation Valve (EGR) before you do anything else. See that your power comes back and you can speed and climb like you used to.

has the cataletic converter been punched out to make it more like a resignator?

Fig. 4: Exploded view of the EGR system and related components for the 4.0L engine (click over pic for zoom)

REMOVAL & INSTALLATION

PFE/DPFE Sensor
This component is found on all engines, and is also referred to as the backpressure transducer.

1. Disconnect the negative battery cable.
2. Detach and label the wiring harness connector from the PFE/DPFE sensor.
3. Disconnect all of the hoses from the sensor.
4. Remove the mounting nuts, then separate the sensor from the mounting bracket.
5. If necessary, remove the EVR solenoid and the PFE/DPFE mounting bracket from the upper intake manifold.

To install:

1. If removed, install the EVR solenoid and mounting bracket onto the upper intake manifold.
2. If applicable, install the EGR tube heat shield.
3. Position the PFE/DPFE sensor on the mounting bracket, then install and tighten the mounting nuts until snug.
4. Attach all necessary hoses and wiring to the sensor.
5. Connect the negative battery cable.

EGR Vacuum Regulator (EVR) Solenoid
The EVR solenoid is mounted either on the same bracket as the PFE/DPFE sensor, attached to the upper intake manifold, or near the EGR valve on its own bracket.

1. Disconnect the negative battery cable.
2. Label and detach the wiring harness connector from the EVR solenoid.
3. Detach the main emission vacuum control connector from the solenoid.
4. Remove the retaining nuts, then separate the solenoid from the mounting bracket.

To install:

1. Position the solenoid on its mounting bracket and install the retaining nuts.
2. Attach the main emission vacuum control connector and the wiring harness connector to the EVR solenoid.
3. Connect the negative battery cable.

EGR Valve
See Figures 6 and 7

1. Disconnect the negative battery cable.
2. If necessary, remove the air inlet tube from the throttle body and air cleaner housing.
3. Label and detach all vacuum hoses from the EGR valve.
4. Label and detach any electrical wiring harness connectors from the EGR valve.
5. Disconnect the EGR valve-to-exhaust manifold tube from the EGR valve.
6. Remove the EGR valve mounting fasteners, then separate the valve from the upper intake manifold.
7. Remove and discard the old EGR valve gasket, and clean the gasket mating surfaces on the valve and the intake manifold.
   

Fig. 6: Cutaway view of a base entry type EGR valve

Fig. 7: Cutaway view of a side entry type EGR valve

To install:

1. Install the EGR valve, along with a new gasket, on the upper intake manifold, then install and tighten the mounting bolts to 4-22 ft. lbs. (20-30 Nm) on 3.8L engines, or to 106-49 inch lbs. (1-18 Nm) on 5.0L engines.
2. Connect the EGR valve-to-exhaust manifold tube to the valve, then tighten the tube nut to 30 ft. lbs. (41 Nm).
3. Connect all wiring or hoses to the EGR valve.
4. Install the air inlet tube.
5. Connect the negative battery cable.

Hope this helps, good luck (remember to rate this comments).

check the EGR by disconnecting it to see if there is a change in the engine at idle

Front of the motor....


Looks like this: