Engine seems to be misfiring, had 6 sets of injectors rereplaced by isuzu dealers, now they say it may be the rail pressure control valve, what is that item, if so how do you fix it or do i have to go back to untrust worthy dealerships? Please note it is an 53 model.

first off check that your fuel pump is sending fuel to injection system. Usually there a release valve on the fuel rail somewhere. check it for fuel pressure.

Plugs get changed at 70,000 miles
I would suggest that you use the OEM
Plugs,they are made by NGK and are special
on my 2004 LS,I don't know about yours.

Clean the MAF Sensor with the CRC Product
for that

Change the 2 front O2 Sensors at 100,000 miles

Check fuel pressure at the fuel rail on engine

The coil you replaced on #6 ,even though you
have a PO306 Code,doesn't mean that was the
bad one. It is a COP Coil or Ford thing, you will
learn as you get involved with them

In some cases, you buy 1 new coil and walk it
from one cylinder to the next.

On single coil codes, you may get lucky,on multiple
codes or a really bad coil you won't

Your not using any fancy test equipment and
unfortunately a lot of repair shops have it and
don't know how to use it,including dealers

V6 or V8 ?

the engine oil pumps are in the rear of the engine(trans out) and behind flexplate /flywheel, were any of these 2 engine oil pumps touched if so the flywheel /flexplate has to be timed to crankshaft position, so you might have it in the wrong position, if your talking about the diesel lift pump (injector pump) that also supplies high pressure engine oil to injectors, after replacing this there is a learn procedure for the rail pressure control valve that is on pump. this can only be done by dealer or some one with Tech2 scanner tool.

P0305 - Cylinder 5 Misfire Detected
P0306 - Cylinder 6 Misfire Detected

When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, The Powertrain Control Module (PCM) or Electronic Control Module (ECM) can determine that a misfire is occurring.

When is the code detected?
- Engine Cylinder #5 and #6 is Misfiring.

Symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/loss of power
- Hard start
- Engine hesitation

Possible Causes:
- Improper spark plug at cylinder #5 and #6
- Insufficient compression at cylinder #5 and #6
- Incorrect fuel pressure
- The injector circuit is open or shorted at cylinder #5 and #6
- Fuel injector #5 and #6 may be faulty
- Intake air leak at cyli

Possible Solution:
- Perform Injector Service
- Replaced Spark Plug #5 and #6
- Replaced Injector #5 and #6
- Replaced Ignition Coil #5 and #6

Hope helps.

ISUZU HAS A RECALL ON LEAKY INJECTORS ON THAT TRUCK GIVE THEM A CALL The injectors use the engine oil at very high pressure to inject the fuel, and semi synth oil just can't withstand these high pressures for very long. It breaks down, loses it's viscosity, and then the injectors won't work properly.
Change the oil to fully synth, and you should see a huge difference. (Do both oil filters while you're at it too). 1. Injectors. Usually the electronics in them fail and cause a miss fire.

2. Injector Sleeves. Causing diesel to leak into the sump and in severe cases the oil/diesel mixture filling up to such an extent that the vehicle actually runs on its own, on the mixture. This can cause the engine to rev to the maximum until all the oil/diesel mixture is burned or the engine basically destroys itself.

3. Rail Pressure Sensor. If the E.C.U cant determine what pressure is at the rail the vehicle may not start or stop running . A fairly simple fix with only the rocker cover needing to come off.

4. Rail Pressure Control Valve. This controls the pressure supplied to the rail. Engine will not start if this control valve is faulty.

5. Turbocharger. A very unreliable unit. Seals usually go after 50000miles.

6. Dual Mass Flywheel. Seldom give trouble but I have seen a few that have. If the new flywheel is taken off and not put back in the same way as the old one (lined up via a half moon shaped mark) the engine will not start as the flywheel sensor will be unable to determine the position of the flywheel.

7. Throttle Position Sensor. Fairly troublesome. Usually no deteriation in driveability but will bring on the engine light.

The engine is a gem when running correctly but unfortunately its a rare occurrence. I think the 02 onwards models had a lot of modifications done to them such as improved injectors etc.

Actually not that hard, but it does require some tools. Normally you will find the fuel rail fastened down in some manner on top of the fuel injectors along that side of the engine. First step is to find the relief valve (looks like a tire valve), be warned that fuel will be under some pressure when you push this valve, do not do this on a hot or warm engine and put a rag around the valve to catch excess fuel.

Remove the fuel rail, then carefully unplug the wiring connector on the # 1 cylinder fuel injector. The injector should come out with a good firm tug, make sure that any O-ring has not been left inside the injector seating area. Place a single drop of oil on the new injector's O-ring and push it into place. Replace the electrical connector, then the fuel rail. Turn on the ignition, but do not start yet - check for any fuel leaks. If none, then start the engine and you should be good to go.

Is this the 3.0 diesel ? Most likely the rail oil pressure sensor is faulty but wont show as a trouble code cos it reads pressures  from 0 - 27Mpa and can  show pressure  even when  its not there ,hard to spot but pull the white wire from the car side of the injector loom by the dipstick and see if that sorts it out-  or the rail oil pressure control valve - this should show as about 20% on tech 2 at idle  if it goes below 15% the engine stops again no code will set .

Most likely I a would suspect the fuel rail had moisture in it. If you checked emissions it would most likely show no HC and alot of 02 and no CO. If it does show alot of HC then I would suspect sticking valves intermittantly . The pinging really points to no fuel issue tho. If you pull the injector connector off and no change then I would remove the fuel rail and inspect. Also make sure the wires are in the correct locations. It easy to get them wrong.

Hello, It should actually be an oil sending unit, and is located on the back of the intake manifold to the left of the distributor. *The P0523 is Oil Pressure Sending Unit Voltage too high *P1693 Generic fault indicating a fault in the bus or PCM/ECM interface *P1682 - I can't find this code Anyways, I will post here all the error codes for future reference. Dodge Cummins Check Engine Error Codes Cycle Key on-off-on-off-on to read codes in odometer display P0002 ECM fuel calibration error P0016 Crankshaft/Camshaft Timing Misalignment/Out-of- Sync P0071 Ambient Temperature Sensor Performance / Rationality P0072 Ambient Temperature Sensor Low P0073 Ambient Temperature Sensor High P0088 Fuel Rail Pressure Too High P0106 Manifold Absolute Pressure Sensor Performance / Rationality P0107 Manifold Absolute Pressure Sensor Low P0108 Manifold Absolute Pressure Sensor High P0111 Intake Air / Charge Temperature Sensor Performance / Rationality P0112 Intake Air / Charge Temperature Sensor Low P0113 Intake Air / Charge Temperature Sensor High P0116 Engine Coolant Temperature Sensor Performance / Rationality P0117 Engine Coolant Temperature Sensor Low P0118 Engine Coolant Temperature Sensor High P0121 Accelerator Position Sensor (APPS) Signal Voltage Too Low P0122 Accelerator Position Sensor (APPS) LowAPPS Voltage Input Too Low P0123 Accelerator Position Sensor (APPS) Signal Voltage Too High P0128 Cooling System Error / Thermostat Rationality P0148 Fuel Delivery Error P0168 Fuel Temp Too High P0169 Water-in-Fuel Detected For Too Long P0192 Fuel Rail Pressure Sensor Low P0193 Fuel Rail Pressure Sensor High P0201 Fuel Injector 1 Circuit P0202 Fuel Injector 2 Circuit P0203 Fuel Injector 3 Circuit P0204 Fuel Injector 4 Circuit P0205 Fuel Injector 5 Circuit P0206 Fuel Injector 6 Circuit P0216 Fuel Injection pump Timing Malfunciton [new injector pump time] P0217 Coolant Temperature Too High P0219 Engine Overspeed P0230 Transfer pump circuit out of range P0234 Turbocharger Overboost Condition P0235 Turbocharger Boost Sensor A Circuit P0236 Turbocharger Boost Pressure Sensor Performance / Rationality P0237 Turbocharger Boost Pressure Sensor Low P0238 Turbocharger Boost Pressure Sensor High P0251 Fuel Injection Pump Mechanical Failure Fuel Valve Feedback Circuit P0252 Injection Pump Fuel Metering Control "A" Range/Performance P0253 Fuel Injection Pump Fuel Valve Open Circuit P0254 Fuel Injection Pump Fuel Valve Current Too High P0300 Multiple Cylinder Misfire P0301 Cylinder 1 Misfire P0302 Cylinder 2 Misfire P0303 Cylinder 3 Misfire P0304 Cylinder 4 Misfire P0305 Cylinder 5 Misfire P0306 Cylinder 6 Misfire P0335 Crankshaft Position Sensor Circuit P0336 Crankshaft Position Sensor Performance P0337 Crankshaft Position Sensor Circuit Low P0338 Crankshaft Position Sensor Circuit High P0340 Camshaft Position Sensor Circuit P0341 Camshaft Position Sensor Performance / Rationality P0370 Timing Reference High Resolution Signal "A" P0380 Intake Air Heater #1 Control circuit P0381 Wait-to-Start Lamp Inoperative P0382 Intake Air Heater #2 Control circuit P0460 Fuel Level Sensor A Circuit P0461 Fuel Level Sensor 1 Performance / Rationality P0462 Fuel Level Sensor 1 Low P0463 Fuel Level Sensor 1 High P0477 Exhaust Pressure Control Relay Low P0478 Exhaust Pressure Control Relay High P0480 Cooling Fan 1 Control Circuit/Open (Low Speed Fan Relay) P0483 Cooling Fan Speed P0500 Vehicle Speed Sensor 1 Circuit, or No Vehicle Speed Reference Signal 1 P0514 Battery Temperature Sensor Performance / Rationality P0516 Battery Temperature Sensor Low P0517 Battery Temperature Sensor High P0521 Oil Pressure Sensor Performance / Rationality P0522 Engine Oil Pressure Sensor/Switch Circuit Low Input P0523 Oil Pressure Sending Unit Voltage too high P0524 Oil Pressure Too Low P0532 A/C Pressure Sensor Low P0533 A/C Pressure Sensor High P0541 Intake Air Heater Relay 1 Low P0542 Intake Air Heater Relay 1 High P0562 Battery Voltage Low P0563 Battery Voltage High P0572 Brake Switch 1 Low P0573 Brake Switch 1 High P0576 Cruise Control Input Circuit Low P0580 Speed Control Multiplexed Switch 1 Low P0581 Speed Control Multiplexed Switch 1 High P0602 Control Module Programming Error/NotProgrammed P0604 Internal Control Module RAM Integrity Failure P0606 Internal ECM Processor P0607 ECU Internal Performance P0622 Generator Field Control Circuit P0628 Fuel Pump Relay Circuit Low, or Fuel Lift Pump Control Circuit Low P0629 Fuel Pump Relay Circuit High, or Fuel Lift Pump Control Circuit High P0630 VIN Not Programmed in PCM P0633 SKIM Key Not Programmed in PCM P0642 Sensor Reference Voltage 1 Circuit Low P0643 Sensor Reference Voltage 1 Circuit High P0646 A/C Clutch Relay Circuit Low P0647 A/C Clutch Relay Circuit High P0652 Sensor Reference Voltage 2 Circuit Low P0653 Sensor Reference Voltage 2 Circuit High P0698 Sensor Reference Voltage 3 Circuit Low P0699 Sensor Reference Voltage 3 Circuit High P0700 Transmission Control System (MIL Request) P0743 Torque Converter Clutch Circuit Electrical P0753 Shift Solenoid "A" Electrical P0837 Four Wheel Drive (4WD) Switch Performance / Rationality P0838 Four Wheel Drive (4WD) Switch Circuit Low P0839 Four Wheel Drive (4WD) Switch Circuit High P1488 Auxiliary 5 volt supply output is too low P1492 Ambient/batt temp sensor volts too high P1493 Ambient/batt temp sensor volts too low P1596 Speed Control Switch always high P1597 Speed Control Switch always low P1652 J1850 Communication Bus P1687 No Cluster BUS Message or No Messages from the Mechanical Instrument Cluster P1688 Internal Fuel Injection Pump Controller Failure P1689 No Communication Between ECM & Injection Pump Module P1690 Fuel injection pump CKP Sensor Does Not Agree With ECM CKP Sensor P1691 Fuel Injection Pump Controller Calibration Failure P1693 Generic fault indicating a fault in the bus or PCM/ECM interface P1757 Governor pressure is above 3 PSI when 0 PSI is requested P1762 Governor Press Sensor Offset Volts Too Low or Too High P1765 Transmission 12 volt supply relay control circuit P2121 Pedal Position Sensor 1 Performance / Rationality P2122 Pedal Position Sensor 1 Low P2123 Pedal Position Sensor 1 High P2127 Pedal Validation Switch 2 Low P2128 Pedal Validation Switch 2 High P2146 Fuel Injector Group 1 Supply Voltage Circuit P2149 Fuel Injector Group 2 Supply Voltage Circuit P2266 Water in Fuel Sensor Circuit Low P2269 Water in Fuel Condition P2502 Charging System Output Voltage P2503 Charging System Output Low P2504 Charging System Output High P2509 ECM/PCM Power Input Signal Intermittent P2607 Intake Air Heater Relay 2 Low P2608 Intake Air Heater Relay 2 High P2609 Intake Air Heater System Performance Hope this will help you. Cheers! Ryan

The normal way that injectors are controlled is via the permanent application (ignition on obviously) to one side of the coil that operates the enclosed piston, and the precisely timed application of ground (negative) to the other side of the coil. The transistors that control this switching under the command of the engine computer are typically contained within the computer itself. Measuring the voltage at the injectors is not productive since the common multimeter is incapable of detecting the very short pulses that activate the coil. Some kind of visual means would be needed to observe this pulse such as an oscilloscope or an engine analyzer equipped with a 'scope.
It's unlikely that all of the switching transistors (or the injectors) have failed simultaneously so either the computer has a problem or there is no fuel being delivered to the fuel rail that feeds the injectors. You should find a pressure regulator that sits between the fuel line coming from the tank that controls the fuel pressure for the injectors. This device seem to be a sore point in many vehicles and can make it appear that the injectors are not working. Many fuel rails have a fitting similar to a tire valve to allow the testing of the pressure being delivered. I would recommend you check this before assuming that the injectors are at fault.