Problem with 88 Bronco II

My daughter owns a 1988 Bronco II that has taken to running poorly, but only intermittently. So, it makes for a tough diagnosis.
Symptoms are that you're cruising along smoothly when all of a sudden the
engine starts running rough, and a strange smell is detected. A short time later it goes back to running smoothly, then the pattern repeats itself.
Can't find any loose plug wires, etc.
Any suggestions...other than selling the old crate? (It's served us well up to this point).
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Invest in a code reader for $25~35. It'll make the diagnosis easier, but it just sounds like a bad connection. If the vehicle has catalytic converter(s) and 02 sensors, could be plugged converter or bad sensor. Dale Randall wrote:

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If it's got one of those TFI distributors I would say it is suspect for misfiring and poor running. They are notorious pieces of junk. I believe Ford only used them for a few years and moved on to a better ignition. Just a thought at least.
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a bad plugwire too. Intermittant misses are almost always a bad plug or wire. If it has been neglected for a while I would put a cap and rotor on it too, they arent that exprensive.
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