Engine light is on, OBD reads misfiring in two spark plugs

First we have to clear up one misconception. Diagnostic fault codes never ever say to replace a part or that one is bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. When a part is referenced in a fault code, it is actually the cause of that code about half of the time. First we have to rule out wiring and connector terminal problems, and mechanical problems associated with that part.

Chrysler hasn't used a stand-alone ignition module for quite awhile. Your truck uses an Engine Computer to run the injectors and ignition system. Those were uncommonly reliable, so that will be way at the bottom of the list of suspects. First we need to know the exact fault code numbers. If you don't have your own code reader, Chrysler made reading them yourself much easier than any other manufacturer. Cycle the ignition switch from "off" to "run" three times within five seconds, leave it in "run", then watch the code numbers show up in the odometer display. You can go here:

https://www.2carpros.com/trouble_codes/obd2

to see the definitions, or I can interpret them for you. Please list those numbers in your reply.

The distributor cap and rotor can cause the symptoms you listed, but the fuel filter is not likely to be bad. Chrysler fuel filters typically last the life of the vehicle, and replacing them rarely solves a problem. Besides the cap and rotor, sparkplugs and wires should be replaced if they haven't been in some time. We can continue looking for the cause of the problem once the common stuff has been handled.

Be aware too that oxygen sensors don't cause a misfire. When they're working properly, they simply report on the amount of unburned oxygen in the exhaust gas, then the Engine Computer makes tiny adjustments in the amount of fuel it is sending to the engine. When an O2 sensor is not working properly, the computer will detect that and set a fault code related to the type of failure. There's about two dozen different fault codes related to the O2 sensors, and they mean very different things. In addition, there's even more fault codes that are set when the computer detects a problem while using the O2 sensors to gather information on how the engine is operating.

Hi,

Your misfires are on cylinder 7 and 3. Have you removed the plugs to check them for condition? Also, often times a backfire is caused by too much fuel. You mentioned it backfires, so take a look through this link:

https://www.2carpros.com/articles/engine-backfires-while-running

The first thing I suggest checking is the fuel pressure. If the regulator isn't doing its job, the pressure could be too high. Here is a link that explains how to check it:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Here are directions specific to your vehicle. The directions include the manufacturer's specs

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1997 Dodge or Ram Truck RAM 1500 Truck 2WD V8-5.2L VIN Y
Fuel Pressure Test - With Test Port
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pressure Testing and Inspection Component Tests and General Diagnostics Fuel Pressure Test - With Test Port
FUEL PRESSURE TEST - WITH TEST PORT
Fig. 7 Fuel Pressure Test Port - Typical

Pic 1

NOTE: Use this test in conjunction with the Fuel Pump Capacity Test and Fuel Pressure Leak Down Test.

Check Valve Operation: The electric fuel pump outlet contains a one-way check valve to prevent fuel flow hack into the tank and to maintain fuel supply line pressure (engine warm) when pump is not operational. It is also used to keep the fuel supply line full of gasoline when pump is not operational. After the vehicle has cooled down fuel pressure may drop to 0 psi (cold fluid contracts), but liquid gasoline will remain in fuel supply line between the check valve and fuel injectors. Fuel pressure that has dropped to 0 psi on a cooled down vehicle (engine off) is a normal condition. When the electric fuel pump is activated, fuel pressure should immediately rise to specification.

NOTE: The fuel pressure test port is used on certain engines only. When equipped the test port will be located on the fuel rail near the throttle position sensor on. A sealing cap is screwed onto the test port.

All fuel systems are equipped with a fuel tank module mounted, combination fuel filter/fuel pressure regulator. The fuel pressure regulator is not controlled by engine vacuum.

WARNING: The fuel system is under constant fuel pressure even with the engine off. Before disconnecting fuel line at fuel rail, this pressure must be released. Refer to the fuel system pressure release procedure.

1. Remove the protective cap at the fuel rail test port. Connect the 0-414 kPa (0-60 psi) fuel pressure gauge (from gauge set 5069) to the test port pressure fitting on the fuel rail.
2. Start and warm the engine and note pressure gauge reading. Fuel pressure should be 3.39 kPa +/- 34 kPa (49.2 psi +/- 5 psi) at idle.
3. If engine runs but pressure is below 44.2 psi, check for a kinked fuel supply line somewhere between fuel rail and fuel pump module. If line is not kinked, replace fuel pump module assembly. Refer to Fuel Pump Removal/Installation.
4. If operating pressure is above 54.2 psi, electric fuel pump is OK, but fuel pressure regulator is defective. Replace fuel filter/fuel pressure regulator. Certain filter/regulators may be serviced separately and some require the replacement of the fuel pump module assembly Refer to Fuel Filter/Fuel Pressure Regulator Removal/Installation for more information.

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Let me know what you find or if you have other questions.

Take care,
Joe