Just to give a brief rundown.

1985 F-150, 351W engine, C6 tranny.

Replaced the factory carburetor with a Holley 500cfm aftermarket (almost direct replacement, just minus the emissions stuff), had to play around with the timing a LOT, and got it running pretty well.

It's got this interesting habit of randomly shutting itself down. The trick is, it ONLY does it while I'm in gear, have been sitting still for longer than about thirty seconds (usual stop-light stop), with a semi-warm to fully warmed up engine. Never while I'm moving, and never when the truck is in park or neutral.

All the lights stay on, it's only the engine that stops. It doesn't sputter and die, it just acts like I turned the key off. It's done this maybe five times now since I bought it, and it's completely random.

Another thing that may or may not be a symptom is, it takes a lot of cranking to get it to start, especially if the engine is warm. It also seems to like starting as I'm letting go of the key, rather than while it's actually cranking. When it dies, it takes a while and a couple of attempts to get it started again, but once it starts it runs fine.

I have purchased a new Ignition Control Module (blue plug) for it, but the weather has been bad so I haven't gotten it installed yet. My question here is, is there anything else I should be looking for while I've got it opened up? Anything else that might come into play as a cause for this?

P.S. I've removed all my emissions stuff (EGR, air pump, etc.) but have already checked for vacuum leaks. When the truck is actually running, it runs great. Good power, good throttle response, etc.

 

This is an intermittent problem like in one of the other posts, and like I said in that one, it's not going to be easy to figure out. I would rig a small light or testlight on the coil + wire, where you can monitor the voltage on the coil. See if the light blinks or goes out when the problem occurs. You could also move it over to the red module wire and monitor the voltage there if the coil + turned up nothing.

 

my two cents....If it ONLY does it in one position, and not at all in the other situations, its not going to be coil or control modual related. Basically, you need to look at the ignition switch under the column, the ignition switch is an electrical contact switch that has the engine run wire connected to the ignition circuit. There could be an "open wear spot" or loose connection while its in the drive position. To test this problem is simple. move the selector of the ignition switch slowly in the run position and test (do not go as far as the start position) with the battery disconnected while useing an multimeter to test in the infinity position. If you get no contact while moving the key ignition switch...while in the run position, then you know you found your problem.

If its the coil, you'll have a problem with long starts and generally bad engine running and no start conditions...a loose wire (dirty and with oil) will also cause this problem.

If its the Control Modual, generally... it'll shut down in any condition and not start at all later on, but it will do it no matter where you are including while driving or sitting in your driveway for no reason at all...after a cool down period, it MIGHT restart.

 

Hmm. Well, I already have a new ICM, and it won't hurt anything to change it anyway. I've been planning on replacing the coil as well, and have thought of bypassing the key entirely (temporarily) to see if that cures it. A friend of mine has an '88 F-150 that has a "dead spot" in his key switch as well, but instead of not running, it keeps all his accessories from working (heater, radio, etc.)

Weather is still too crappy and wet right now to do too much, but I'm going to try and get some of it done today before we get our 6 inches of snow tonight. Thanks for the replies though.

 

Well, replaced the module and it's running a LOT better now. Starts somewhat easier for the most part, but is still giving me long cranking times other times.

Cleaned the contacts on my coil too, they were kinda nasty looking, but that didn't seem to do anything for driveability.

I will probably be replacing the coil soon as well. Since the housing is pretty rusty I figure it's about time to replace it, even if it isn't what's causing me problems.