Have 88' BII, 2.9ltr-5spd. Have new Distributor Cap, rotor, new plugs and wires. Ignition Module is bout 2 years old as well as the battery. Coil...AND Alternator around 4 years. Anyways, after i get up to operating temperature(Round 190*)the thing develops a "miss". AND, it doesn't do it all the time it's intermittent. Depends alot on the outside temperature. Could it be the coil "breaking down" or maybe the alternator cutting on and off? Thanks!

 

If this vehicle is fuel injected, I would pull the codes and see what they say. Remember the coil is common to the whole engine, so it would really run rough if it was at fault.

If you suspect the alternator, put a meter on the battery and see what the voltage is with the engine running. It should be around 14v.

I would also find the engine computer, and unplug the large plug and plug it back in several times incase there is any corrosion on the terminals.

 

I am having a similar issue with my 1979 f250 with standard <NOBR style="COLOR: darkgreen; FONT-SIZE: 100%; FONT-WEIGHT: normal" id=itxt_nobr_20_0>ford</NOBR> electronic ignition. It had a stock 351M which I swaped for a 400(M?) using all the accesories and ignition from the 351M. I have had to replac the coil and ignition module 3 times over 7 years or so, and in the past 3 or 4 months, it has been a problem every time I drive it.

Most recently what I am experiencing is that after what seems to be a consistant 37 minutes of good running time and normal driving, the engine will just shut off, as if the ignition had been turned off. At that point, the engine will not start or even fire. I have confirmed that I am getting fuel <NOBR style="COLOR: darkgreen; FONT-SIZE: 100%; FONT-WEIGHT: normal" id=itxt_nobr_21_0>pressure</NOBR> into the carb, I seem to be getting at least some spark, based on a simple "screwdriver in the plug wire" test. Also, at the point that the engine dies, the coil becomes abnormaly warm. In a few instances, the ignition module has been warm too.

After a cooling off period, which was 30 minutes a few months ago, and now seems to be 3 hours, the truck willl start just fine and run for another 37 minutes, give or take. In cases where I drive the truck for less than 37 minutes, say 15, and let it sit for say 15 mintues, it fails to start, with apperent fire, but no ignition, and the coil is warm.

I suspect an issue with wiring, but don't really know where to begin. As a thought, I've contemplated just getting a single unit distributor ignition, or an MSD system, including wiring harnes, and just bypassing all of the stock igintion stuff. But I lack in experience or in depth understanding or the system, so I don't know what my best bet would be, or even where to start. I don't want to just jump in and start clipping wires, so I'd really appreciate any advice that anyone has.

 

With your stock Duraspark 2 system, you should have a round coil.
At idle, check the voltage at the coil positive. It should be alot LESS than battery voltage at idle, like 8 volts or so.

If the coil + is getting full voltage, 14 VDC, the coil could be getting to hot.

Jim

 

Also, if you are getting aftermarket ignition boxes, some people have better luck with the motorcraft modules. Some even go to the junkyard and get the motorcraft box.

The msd is not hard to install. They have a very good site with all their instructions online if you want to look at what it takes first.