I have a 96 F250 Powerstroke. 115K miles Engine started misfiring randomly and then clears up and repeats this a couple times every few miles. Check engine light goes on during misfires. I'm thinking its the valve cover harness or connectors. I haven't tried my code reader but it may not be the right one. Is there a "shade tree" mechanic way to determine which bank is misfiring? Thanks.

 

If you look under your hood with it running and see the 4 plug in look for all the connections for burnt, black connectors. Also you can (or I did but only for a couple seconds) unplug the 4 while it's idling and if it gets worse you know those 2 injectors are good.

 

And check your oil level. Mine acts up when the oil gets low or too old.

 

I unplugged the connector while running and that identified the bad area for me. Mine actually broke the wire at the connector for the glow plug and the wire was intermittently shorting out. It was a mess to diagnose because it would run fine while the GP relay was on and then fall to pieces after. Initially, though, I had some symptoms like you describe. If you can afford it, definitely go with the Ford UVCHs in my opinion.

 

I had the IDM go bad on my truck about 6 months ago. I did not have the equipment to test the IDM so I had to verify everything else worked before I put the 800 bucks into a new one. The IDM is placed in a bad place. Its located on the driver side fender out in the elements you pick up off the road.

With that being said I will try to remember how I narrowed it down to the IDM in the first place.

I will note that like lindstromjd said check your oil. It is imperative that you keep up on oil changes, and levels with these trucks.

 

What I learned from ReBilld after my little fiasco was that the IDM will shut down a bank if it picks up a short in the glow plug system. So it is really worth pulling the VCs and checking all those connections before you invest in an $800 IDM. I didn't find it that hard to do really. I kept expecting it to be harder from some of the things I read, but getting the VCs off wasn't really bad.

 

I haven't had to time to try to fix this yet. I'll definitely check the oil level first. My code reader of course couldn't read the codes. At idle it sounds perfect, so pulling the connectors at idle wouldn't tell me much. Last time I had problems with this thing it was the CPS and damm it took me a long time to diagnose it, these powerstrokes are a PITA to diagnose a problem when they run bad. Hopefully tomorrow I'll get to work on it. After the oil check, I'll start checking the valve cover wiring.

 

800$....somebody got hosed!!!

 

To check the IDM unbolt it and unplug from harness. Shake it and if you hear water it's shorted out. Mine went bad and shut down the front 4 cylinders.

 

I pulled the driver side valve cover off. all the wiring and connectors look perfect. How hard is it to get the passenger side off? Looks very close to the AC box.

 

Since you have a 96, the little box on the side of the A/C box should come off. Earlier 94-95 ones don't come off.
And it's not about how the wiring looks physically, it's about how it performs under a voltage test.