Forgive me for chiming in - you guys are both light years ahead of me on this subject, but something Bill said earlier in the thread struck me.
Bill has had basically the same problem (unpredictable performance) with two different engines (Pinto & Zetec) and two different fuel delivery systems (carb & EFI). So let's identify what these two setups have in common, and look for a problem there.
Bill will have to answer that question, but I am thinking fuel tank, possibly fuel filter, fuel lines, fuel pump. Could we have some debris in the fuel system randomly influencing the results?
I hope this helps. Hang in there Bill!
Todd, believe me, I've given this considerable thought.
Here is the background. During the initial rebuild of the car, the tanks were cleaned, stripped and recoated with POR 15 tank sealer, which seems to be holding up. The tanks and plumbing are dead stock. There is a fuel pump mounted under the trunk floor. Initially, it was a Bosch, intended for use in a Volvo 240. It is now an OEM Ranger/Mustang replacement. The two are quite similar, the Ford unit has about twice the flow. I've measured the flow at zero pressure, it is very impressive. Two small steel bodied, 5/16" filters are used, one before and one after the pump. Return flow has always been to the passengers side tank. 5/16" O.D. steel tubing was used for the supply and return line. Initially, 1/4" O.D. was used for return. The 1/4" line was presenting considerable back pressure, the 5/16" line stopped that.
In short, the only common components are the supply fuel line, which is new and was plugged for installation and the fuel filters. They have been replaced with new ones of the same description. I don't see how the problem could be with the filters as the issue presents itself across the rev range, with idle and off idle performance a biggie.
Jarrid has inspected my tune and found a few problems. He also suggested a minor wiring change, jumping between too computer terminals, which should help stabilize the tune. Well, nothing is ever that easy around here. Way back when I wired the computer, I screwed up a couple of wire terminals in the computer connector. So a couple of then unused wires were left out. Now that they are needed, I had to order some terminals in order to finish wiring the connector, they should be received tomorrow.
I am interested in determining the problem, so I am holding off on the tuning change until I can implement the jumper mod. The bulk of Jarrid's tuning changes are designed to trouble shoot the system and if the jumper works, I'd rather skip that exercise and return to tuning. But those changes may represent the quickest way to a good tune. I'll just have to wait and see.
Bill