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1995 Ford Windstar Van Misfiring Under Load with PO340 Code - Solutions and Diagnostics

Model: 1995 Windstar Fault Code: P0340 Posted: 2009-03-14 13:45

I own a 1995 Ford Windstar van with 187,000 miles on the odometer. Approximately two weeks ago, the vehicle began displaying a PO340 diagnostic trouble code. I replaced the cam position sensor, but the issue persisted. Initially, the engine ran rough upon startup, smoothing out once in motion—however, when driving uphill or under load, it would suddenly misfire. Accelerating with the throttle helped stabilize the performance temporarily. I then replaced the fuel filter, which improved the situation: the vehicle now runs smoothly at idle and briefly roughens slightly when shifted into gear before stabilizing. However, this improvement lasted only about three days. The engine has since started misfiring again under load—particularly on hills—indicating a recurring issue. I'm seeking advice on what to check next or where to begin diagnosing the problem. Could it be related to ignition components, fuel delivery, or sensor calibration? Any insights or recommended steps would be greatly appreciated.

Related fault codes
P0340
Comments (5)
Anonymous 2009-03-14 16:30

Several potential causes exist. How long has it been since the last tune-up? Is this a 3.8L engine? EGR ports can partially clog and contribute to misfires under load. Also, did you inspect the cam synchronizer for damage or wear after replacing the cam position sensor?

Anonymous 2009-03-14 19:52

Yes, it's a 3.-8L engine. The vehicle hasn't had a full tune-up in over 60,000 miles. After replacing the cam position sensor and resetting the ECU, the PO340 code has not returned. However, it still runs roughly for about 30 seconds when shifted into gear before stabilizing—no misfires at idle or under light throttle.

Anonymous 2009-03-14 19:55

EGR issues typically affect idle roughness rather than misfiring during partial throttle. A faulty ignition component, such as a bad spark plug wire, may be more likely to cause the observed symptoms under load.

Anonymous 2009-03-14 20:00

A complete tune-up—including spark plugs and wires—might resolve the issue. Given the age of the vehicle and lack of recent maintenance, this is a strong starting point for troubleshooting.

Anonymous 2009-03-15 07:10

The ignition coil is another possible culprit. Without actual testing, it's difficult to confirm, but I recommend performing a full tune-up as a first step to rule out common failure points.