P0743 and P0307 Codes - 1999 Dodge 25-00 Van 318 5.7L V8: Misfire and Transmission Issues Explained
I own a 1999 Dodge 2500 van with a 318 5.7L V8 engine. The vehicle runs fine on highways for up to 40 miles, but I notice occasional bucking—especially when driving at lower speeds or idle. At slower speeds, the bucking becomes more severe, almost as if the engine is about to stall. Occasionally, the check engine light blinks, which seems to indicate a misfire. However, when I connect an OBD2 scanner, I either get no codes or only see P0743 (Torque Converter Circuit Malfunction), which appears consistently but can disappear after a short time. I've also recently seen a temporary P0307 code (Cylinder 7 Misfire Detected), which went away after a restart. I’ve already replaced all spark plugs and wires, installed a new fuel pump, cleaned the injectors, had fuel pressure checked, and replaced the fuel filter—none of these resolved the issue. I've read in another forum that a cracked cylinder head might cause smooth highway performance but poor idle or low-speed behavior. While this hasn't been confirmed on my vehicle, I'm looking for other possible causes. Could the P0743 transmission code be directly causing engine misfires? Or is it more likely that an engine issue (like a misfire) is triggering the transmission fault? Any insights or troubleshooting steps would be greatly appreciated. Thanks! Garren
The P0743 code indicates a problem in the torque converter circuit—this could stem from a faulty solenoid, wiring issue, or internal failure within the transmission. I recommend checking the electrical connections and solenoids first. If the issue persists, it's best to have the transmission inspected by a qualified dealer or specialized transmission shop. In the meantime, consider addressing any engine misfires before focusing on the transmission, as poor engine performance can affect shifting behavior. Good luck—please update us if you find a resolution.