Bad miss on start

I have an87tc motor in a 91 Mustang. It has all new motorcraft ignition parts. On cold start ups, (below 50 degrees), it has a bad miss for about 2 minutes, then runs like a champ. After putting new motorcraft ign. parts in it now runs rough for a minute or so regardless of temperature. If I scan it after it runs rough, I get a 14 code, pip failure. I've been studying the skis for both the 87 and the 91, I noticed that the 87 has a ballast resistor on the green wire between the coil and the #4 pin on the computor. The 91 has no resistor indicated and right now there is not one on the car. Could this possibly be the source of the miss? I'm getting very frustrated. I've been spending too much time curled up in the fetal position, sucking my thumb in the garage.

Change the pip or the whole dist.

That circuit with the resistor (22,000 ohm, I think) is the IDM circuit. Yes, there should be the resistir there,but I dont think that is the cause of your problem.

COde 14 can be caused by a bad PIP, but more often by bad plug wires / cap / rotor / plugs radiating RFI/EMI, which interferes with the low voltage PIP signal. I know you just did a turn up with Motorcraft parts, but recheck to be sure all the lug wires are seated completely on the cap and plugs, coil, etc. Rare, but I have heard of plug wires being bad out of the box.

When it runs rough, does it seem lean? Could be an ECT telling the EEC coolant temp is too warm. Measure ECT resistance with motor cold. Resistance should be about 55,000 ohms, roughly, with 70 deg coolant. Id ohms are significantly lower, like 20,000 @ 70 deg, ECT is bad. An out of spec ECT often wont set a code unless it is really wacked out.

------------------
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 02 Taurus Vulcan(wifes car)

Thanks for the insight, guys. I ran new pip, spout,ground, and idm wires right to the computor yesterday, and it ran a little better, but yes Jeff, I spit out a 41 code. I did change the act, but I never thought about the ect. That makes a lot of sense, because that sensor is from the old motor before the swap, and that motor always spit out the 14 code. I'm going out right now to measure it. Thanks again.