I've got a '96 powerstroke with an intermittent problem. A few days ago the engine started having episodes where it runs very rough. The check engine light comes on when these events happen. The onset and resolution of the episodes is instantaneous, like turning on or off a light switch. They have happened at idle shortly after start, and also at cruising RPM when the engine is fully warmed up driving down the highway. The duration is from less than a minute, to several minutes idling, to the latest event in which the engine ran for 30 minutes plus and never resolved. The engine will idle at reduced RPM when this is going on, and will rev up, but is very rough and doesn't develop any real power. Revving the engine doesn't seem to make any difference toward clearing up the problem. Fluid quantities are normal, and pressure / temp guages are normal. The engine runs normally when these events are not in progress.

Right now the truck is at a local shop in the vicinity of where I stopped driving last time this started a couple of days ago. The mechanic said he would check the engine diagnostic codes & let me know what was going on. When I spoke with him later he said it showed no codes, and he wants to spend some time troubleshooting. This is raising a red flag for me. Doesn't the computer store any code which triggers a check engine light?

Here's a little more history. A month or so ago the engine developed a serious oil leak from the lower left rear of the engine. Turns out the high pressure oil pump housing cracked. A local diesel shop replaced the part. When I picked up the truck he said he thought I might have more of a problem, and that the truck started running rough during test running after he replaced the pump. At that point I had never experienced what he described, and when we started the truck it ran fine, so I drove away. It ran fine for a few weeks until I started having these problems a few days ago.

Any ideas about what's happening here, or thoughts for me to consider?

1996 F250 7.3 Powerstroke
95,000 Mi.

 

under valve cover harnesses fried?
plug into vc gasket fried?
check those...

 

pushin dirt r u, you are absolutely right. The wiring under the valve covers was the problem. Thanks.

 

That was a fast fix bizz60. Did you replace the harness or rebuild the connector?

Welcome to Ford Truck Enthusiasts.

 

Had to replace the #2 and #4 injector wires, and the primary connector plug on the valve cover gasket/connector was cooked, so also was replaced. The local garage I first had look at the engine must not have had the right analyzer. They said they didn't find any fault codes and could find nothing obviously wrong, so they threw in the towel and recommended I take it elsewhere. When I subsequently took it to my diesel shop he was able to retrieve the fault codes and buzz test the injectors which pointed to the problem area. Runs like a champ now. By the way, in my description of the problem I mis-stated that the truck had been in the shop earlier with an oil leak because the high pressure oil pump housing had cracked. For the record, it was actually the engine oil cooler housing.