* Injector #7: A clogged or faulty injector on cylinder #7 will prevent proper fuel delivery, causing a misfire. You can try a fuel injector cleaner additive in the fuel tank, but a more definitive test involves checking the injector's spray pattern (requires specialized tools) or swapping it with another injector to see if the misfire moves.
* Wiring to Injector #7: Even with new wires to the distributor, there could be a problem with the wiring specifically leading to injector #7. Check for broken wires, loose connections, or corrosion near the injector connector.
* Vacuum Leak: A vacuum leak can disrupt the air/fuel mixture, especially noticeable at idle. Inspect all vacuum lines, particularly those near the intake manifold, for cracks, holes, or loose connections. A hissing sound around the intake is a good indication.
* Compression Test: Low compression in cylinder #7 indicates a problem with the piston rings, valves, or head gasket. This is a crucial test to rule out internal engine damage. A compression test will give you a quantitative measurement to confirm cylinder health.
* PCM (Powertrain Control Module): While less likely given you've already changed some ignition components, a faulty PCM could still cause a misfire by incorrectly controlling the fuel delivery or ignition timing for cylinder #7. This is a more difficult diagnosis and typically requires professional tools.
Troubleshooting Steps:
1. Compression Test: This is the most important next step. Low compression in cylinder #7 strongly indicates an internal engine problem.
2. Injector Check (visual or swap): Visually inspect injector #7's spray pattern if possible, or swap it with another injector to see if the misfire moves.
3. Vacuum Leak Inspection: Thoroughly check all vacuum lines for leaks.
4. Wiring Inspection (Injector #7): Carefully examine all wiring leading to injector #7 for damage.
5. Fuel Pressure Test: While less likely to be the cause given it's only one cylinder, a low fuel pressure can affect all cylinders.
Before starting any work:
* Disconnect the negative battery terminal to prevent electrical shorts.
* Consult a repair manual specific to your 1996 Dodge 250 van with the 5.2L engine. A repair manual will provide detailed diagrams and procedures.
If you're not comfortable performing these tests yourself, take the van to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and efficiently. Mentioning you've already replaced plugs, wires, cap, and rotor will save them time.
