This 98 Ram 1500 hasd a 5.2 L 81,000 miles came in for running rough and codes p0300, p0305, p0307, p0308. We did the obvious changed plugs with oem, aftermarket cap and rotor and wires. I made sure wires were routed as per bulletins, Readjusted distributer synch, also found intake leaking at lower plenum.Replaced intake gaskets. Truck seems to miss mainly on 5 and 7 but is random more so hot than cold. miss comes and goes.
Checked exhaust back pressure under 2psi at 2000 rpm

This 98 Ram 1500 hasd a 5.2 L 81,000 miles came in for running rough and codes p0300, p0305, p0307, p0308. We did the obvious changed plugs with oem, aftermarket cap and rotor and wires. I made sure wires were routed as per bulletins, Readjusted distributer synch, also found intake leaking at lower plenum.Replaced intake gaskets. Truck seems to miss mainly on 5 and 7 but is random more so hot than cold. miss comes and goes.
Checked exhaust back pressure under 2psi at 2000 rpm


hi i also have a 98 ram 5.2 liter and my truck was misfiring like that and i took it to the dealership and asked to check the timing on the engine and my timing was off three degrees. they flashed and reset the computer and it works good now

jeez ,The plenum gasket is the main cause! Try using some Techron + for a few weeks and see if the misfire goes away. You got major crud build up on the valves or a burnt valve or seat. Hopefully the Techron will clean them up. It worked on mine. And also depending on how long the plenum gasket was bad, it will ruin the cat. converter. How exactly did you check the back pressure?

micahw, check your plenum gasket. I bet it's bad! The dealer probably flashed it with software that retards the timing to mask the plenum prob. that all dealers know about. It is called the Death Flash! Google it and you will see what I mean.




And BTW you both should do a search for a TSB that relates to how to route the sparkplug wires, which will also cause misfires.