3.8 CFI driveability issue October 01, 2011, 01:29:35 PM It's not a T-Bird or Cougar, but I'm hoping someone can help me with an issue. I picked up an '84 Mustang convertible with a 3.8L V6 from the local Goodwill auction. Both fuel pumps were out and it had about 2 quarts too much oil in it. I replaced the fuel pumps and did an oil change. While I was at it I put in new plugs, changed the O2 sensors (original), and the IAT (covered in oil).When I first start the car it runs great. After about 20-30 miles of driving it will start to develop a miss. It becomes a solid but random miss that continues as long as I’m driving the car. At highway speed the miss occurs at different intervals and for varying lengths of time. The problem is much worse at low speeds, so much so that it wants to stall at idle.Any suggestions would be appreciated. Thanks! Quote Selected
3.8 CFI driveability issue Reply #2 – October 01, 2011, 08:12:44 PM Quote from: softtouch;368971Codes?X2Sounds like probably something in the ignition is failing when the engine is at full operating temp... If it has a erratic ignition code, the problem is likely either the TFI module or the PIP inside the dist... Quote Selected
3.8 CFI driveability issue Reply #3 – October 03, 2011, 10:47:06 AM It didn't show any codes last time I scanned it. (None saved, none running) I'll drive it again and scan when it starts acting up. Quote Selected
3.8 CFI driveability issue Reply #4 – October 03, 2011, 12:41:16 PM Quote from: 87Cougar5pd;369096It didn't show any codes last time I scanned it. (None saved, none running) I'll drive it again and scan when it starts acting up.Did you get code 11 ? Quote Selected
3.8 CFI driveability issue Reply #5 – October 06, 2011, 08:12:15 PM Drove the Mustang tonight and right at the 20 mile mark it started acting up. A KOEO scan revealed codes 11 & 63. My scanner defines code 63 as "TPS circuit below minimum voltage".When I first bought the car it didn't want to start and ran very poorly when it did. I checked the TPS because I know they are pr0ne to causing problems. At the time the engine was cold and I didn't get any "out-of-range" readings with the OHM meter, just a steady rise and fall when working the throttle. A quick sweep of the TPS with my OHM meter tonight with the engine hot shows several dead spots throughout the range.Has anyone heard of that problem being temperature related? Quote Selected
3.8 CFI driveability issue Reply #6 – October 07, 2011, 12:42:36 AM Heat kills electronics. Might have just went bad after getting it back on the road too.You could try adding and checking grounds. As wires get hot from a load, their capacity suffers. If your ground is too weak, it might be fine when you start it, but as it heats up or if you run your headlights for a while, it will lose capacity. Quote Selected
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