Distributor is new, we think it might be a resistor going to the ignition coil
Code 18 is a serious code. You said the distributor was "new". What does that mean? I bet it's a rebuilt Cardone? Had the same thing happen to me on my 2.9. Had all sorts of problems bucking and jerking. Decided to replace the pickup inside the distributor. You have to tear the distributor apart to do this. I wasn't careful trying to pull the gear off and broke a couple of the teeth. No one in the whole country has just the gears, eve n though they do list them.
I finally figured my best option was to get a whole "new" rebuilt distributor. Got a rebuilt one from Cardone, they are pretty much the only game in town no matter what store you go to. Installed it, and my problems actually got worse. How can putting a rebuilt distributor in place make my problems worse? I pulled it back out, looked down inside, the module in this rebuilt distirbutor had never been replaced. I paid $80 for this thing, and I didn't even get a new module. CAREFULLY took the gear off this distributor , took it apart, it was full of old sticky black carbonized oil, ,they had never even took it apart. They had cleaned it up on the outside and put it back in the box. I put the new module in it that I had bought for the one I broke, cleaned it up and oiled it, put it back together and it ran smooth.
When I went to convert my 2.8 to duraspark II, I looked and looked, Cardone is the only people who had them. So took a chance, everything seems fine so far, but it's a crap shoot with them. Our best chance to get a good rebuilt distributor from them is if someone turned one in and there was nothing wrong with it in the first place.