I have a '79 351M, and every single time that a guy starts it, and goes to back it out of the shed/drive it out, it will stall. Might do that a few times. Idle speed seems to be fine - I'll check it - should it be around 700? I hate it when you are approaching a stop sign, and the thing stalls. Or if you back off the gas for some reason, and it stalls. Doesn't do it all the time. Definitely worse when it's cold, but it'll do it when it's warm.


My other problem - you can be just driving along, and the engine stops. It has a C6, and if you're moving fast enough that the engine is still turning, if you turn the key off, and then back on, it will run again, drive just like normal. It does not backfire when this happens. I replaced the coil over winter, and this problem got a LOT better.


Are the two problems related, or might I be chasing two gremlins at once? I saw a post about the ICM..... is that on the inner fender?


Rodney

 

Icm, coil, plugs and wires can cause stall problem. Also a stuck carb float or dirty carb and filters. These are the simplest culprits to check and fix.

 

Yes icm, is on driver side fender.

 

If you're replacing the ignition module, two tips:

1. Spring for the Motorcraft brand module, rather than one of the aftermarket pieces. On this part, there's a huge difference in reliability.
2. Duraspark ignition modules are identified by the color of the grommet around the wires. The earlier Duraspark I modules had black or green grommets. The later Duraspark II ones had blue. Wiring is not compatible between the different generations. They switched to the blue grommet version in, I think '76, so you should be in good shape there, as long as your engine/wiring hasn't been swapped from an older truck. If the smaller connector with the red & white wires is only those two, you should be in good shape: the earlier ones also had a blue wire on that plug.



If you can't find the Motorcraft module at your local parts store, RockAuto carries it. It's $43 vs the ~$20 that aftermarket brands run, but is worth every penny of that.

 

If the idle speed seems fine and the truck isn't running choppy, i would suspect a vaccum leak

 

We replaced the coil within the last few months, and it dies MUCH less than it did before, but it still does it. In another thread I was talking about moving the distributer, so I was trying to find the timing. In my process of doing that, I figured that the light should come on at regular intervals, and it didn't. Every so often it would 'miss' because there was no spark, according to the timing light. Does that point to the ICM?

 

Check the Distributor Cap contact on the inside, long ago I had something similar happen to me and one of the contacts was actually broken off. Not sure how it happened so I replaced the rotor and cap assembly and for less than $20 problem fixed with no further problems.