I have a 71 Challenger R/T 383 auto.Everything electrical from the fire wall forward is new.The red power wire under the dash has been repaired at the bulk head connection.

My problem is that most times,but not all the of the time it will not start after it has been driven a short distance.It will crank and when you turn the key to off position it is like one cylinder fires.It feels like a slight bump.You can even feel the car twitch or jerk a little.Last night it shut off while setting at an idle in gear.I had driven it about 10 miles.After setting for an hour it started,I drove it a mile shut it off and it wouldn't start.

I have replaced the balast resistor and coil so far.I am thinking maybe it is the orange box on the electronic ignition.

Any help would be greatly appreciated.

Thanks,Dave

I would be inclined to think ECU but I would recheck that it's grounded good & the next time it acts up grab a jumper wire w alligator clips & jump from the coil negative primary terminal to ground repeatedly like Morse code & see if the coil to dist wire held 1/4" from ground has fire(key "on") and to double check take off the coil neg to ECU wire off of the coil neg terminal & again retry it. An ECU is supposed to default in the open position but cant assume nothing. if you have fire I would highly suspect the ECU & if bad I would not get another orange one

What box would you recommend?

Chrome box. Nothing but that on my rides...

Chrome ones are very reliable but I dont know how much they are(it's a MP item so might be pricey) and a guy on here on a thread yesterday had stock ones(blue/black depending on if 4 or 5 pin) for $15 + the ride,downside would be the shipping wait and I have yet to see any significant difference in any ecu's(performancewise) even the FBO as long as they are not acting up which yours definitely is.

I bought a chrome box but that wasn't it.At this point it looks like the magnetic pick up in the distributor.When hot the trigger would turn freely on the dist shaft.It was held in place,supposedly, with a tiny roll pin.Is this poor design and quality by Mopar Performance?

The roll pin assy is solid/trouble free. There's no pin in there?