Hope everyone has a safe Memorial Day weekend! I have a 1996 F350 Crewcab SRW, with a 7.5/E4OD combo. I have been having an ongoing engine miss, only when the air temp is cold (50 and lower), the miss is in the 1500-2000 rpm range, and once the engine coolant temp gets up to operating temp (195 or so), it runs very well. I had not experienced the miss or any running problem, now that warmer temps are here. However, yesterday morning was colder than normal for this time of year, and I went out to fire up truck and head out on a round trip of 200+ miles. When I started the engine, it misfired badly and set off the CEL! I shut it off and opened hood and checked engine oil and coolant, and did a visual, found nothing out of order. I fired it back up and ran it until coolant temp topped out and left on trip. Truck exhibited no problems once warming up. It got it's usual 7-8 miles per gallon. I checked codes once home and got one I have never seen, P0420. I am going out now to fire it up again, it's cool outside maybe 55, and see it it reoccurs! Weird!! Thanks! Dale

 

Sorry for overlooking your post. The weekend has been busy so lots of posts push yours to the back.
Hopefully someone will chime in with exact code, but my suggestion is, because of the trucks age...

New air temp sensor, coolant sensor, and o2 sensor/s. maybe a complete tuneup as well with MSD coil and decent plug wires. This may not fix your issue completely, but def help with power and mpg.

 

Thanks for the response! I did as I stated, and went outside and fired up the truck when the temp was cool, and it repeated the misfiring scenario. I had already replaced the ECT sensor a few months earlier, as well as the Air temp sensor, but my gut kept telling me that the ECT was either the wrong one or defective, so I had bought another one. So, I replaced the ECT and refilled coolant and fired up truck again, and it ran fine, no miss! Now so far it has not repeated the cool temp miss deal, so I am hoping that took care of that. However, I am afraid that the Cat Convertor is on the way to plugging up. The DTC P0401 and P0420 still set the CEL. I am going to drop the Cat on take a look soon. Oh and for the suggestion of installing a MSD coil, that was one of the first things I did to this truck, and it died after 2 months, and was replaced by a generic Balkamp or Standard coil. When I fisrt got this truck it ran ok, but was a bit of a dog, and I noticed it had the OEM wires etc. So I changed out the wires, cap, rotor, plugs, then the coil. The plugs had 122,000 miles on them! Also the truck never warmed up, and I found a 160 degree thermostat in it, and put in a 195 degree one. Well, thank God I am retired and have time to screw with this truck!! Thanks! Dale