O2 Liberty 3.7L Engine: Injector Circuit Faults in Cylinders 2, 4, and 6
After an 8-month engine rebuild, a customer brings in their Jeep Liberty with a 3.7L engine exhibiting rough running and persistent fault codes for cylinders 2, 4, and 6 — all on the same side of the engine. The issue is unusual given that these cylinders are grouped together. Despite clearing the codes multiple times, they return immediately. What steps should be taken to diagnose and resolve this problem? Possible causes include wiring issues, faulty injectors, or electrical components such as capacitors connected between injectors and ignition coils.
This issue sounds similar to what I'm experiencing. I haven-'t confirmed the root cause yet, but I've noticed a capacitor (Capacitor 2) that connects between the injectors and ignition coils for cylinders 2, 4, and 6. It's possible this is the source of the problem. I recommend swapping Capacitor 1 with Capacitor 2 and then retesting using a Noid light to see if the injector signal changes side-by-side. The capacitors are typically mounted on valve covers between cylinder pairs: 3&5 and 4&6. Additionally, perform an ohm resistance test on all injectors to ensure they're functioning properly and not causing short circuits. A variation of up to 0.3 ohms should be acceptable across the injectors.