It's a 74 2.0 and it has an MSD box.

The other day it would not idle all of a sudden. I was stopped and it was revving about 800 rpm give or take a few. Then the idle dropped a lot to the point of the alternator light coming on. Then it recovered and idled up to 1500. Then it dropped back down. It did this for a while and then went back to normal.

Then as I was driving at around 45 or so in 5th gear it would lose power like I turned it off and then came back to life. It doesn't do this when I accelerate. It does this in any gear, any rpm.

It also feels sluggish without much will to move. It's never done that before. Then it got better and worse, on and off.

Last but not least if I stop the car and turn it off, it keeps running. The gauges turn off, the tach goes to 0, the radio etc turns off, but the engine keeps running. Until I step on the brake pedal. Then it turns off.

I'm not sure if all this is interrelated but I don't know how to go about finding the source of the problem. The timing is adjusted, the filters are new, the fuel pressure is correct. It doesn't matter if the throttle switch is plugged in or not, and the ECU idle control know does nothing to counter these effects.

Any pointers?

Thanks guys

the Sudden Loss Of Power (SLOP) is a classic MSD symptom, especially if you're driving your tach with the MSD TachOut port and the tach signal is unchanged.

where did you connect your Switched +12 and the direct-to-battery wires?

the keeps-running symptom has been known to be caused by - of all things - bad connections to the front turn signals. wonky grounds can affect it too.

BTW - 45 is *WAY* too slow to be in 5th gear !!! your cylinder head temp will SKYROCKET!!! 5th is a HIGHWAY gear ONLY!