1997 Ram 1500 extended cab 4x4. It has the 5.9 v8 with 299,887 miles. The issue is. It seems to run fine when the motor is cold, But once it gets up to temperature it starts to miss like some of the cylinders aren't firing. It is more pronounced and frequent on the freeway when up to speed in overdrive and giving a little bit of gas.


This started about 4 weeks after changing plugs and wires to resolve another symptom (which turned out to be fuel pump). Drove it for 4 weeks and ran like normal. Drove from Michigan to KY where it sat 24 hours then drove to Georgia. The problem started shortly before reaching destination (about 5 hours)

It has new plugs and wires (except two plugs which were stuck and I didn't replace for fear of snapping them off) I realize there is a slight chance that one or both of these plugs are fouled but is there something else that could be causing this that I can check before running the risk of breaking those plugs trying to replace them.

. My experience has been to only use the same Champion spark plugs that came in the truck, on Dodge products. Other brands of plugs have broken down under heat rapidly. It was the only factor that kept the trucks from starting. Be sure to use a very thin coating of antiseize compound on the threads and don't overtighten, since the antiseize is a lubricant. I would definitely try and replace the two old plugs--just go easy.

. Replace the fuel filter, if it hasn't been changed in the last 25,000 miles.

. Check/replace the Engine Coolant Temperature (ECT) Sensor, which affects fuel injector pulse width. The ECT Sensor is a temperature dependent resistor (thermistor), whose resistance decreases as the engine coolant temperature increases. It provides a richer mixture when cold, leaner mixture when hot. They become corroded, due to not changing the coolant frequently enough, flood the engine, and waste a tremendous amount of fuel.

. Check for codes, even if the CEL has not come on yet.

The plugs are likely the main problem. The two old plugs could be misfiring badly.

Thank you very much for the quick reply. I will give these a shot. One more quick question though. Should one of these plugs break (fingers crossed). What kind of a headache am I looking at?

They shouldn't break, if you work them properly. Apply PB Blaster or Kroil repeatedly and work them carefully. Try removing them when the engine is stone cold, in order to reduce the possibility of stripping the threads.