Rough idle?

[joecap409]

My 86 rough idles and at 25mph to 35mph the rpms jump up and down

 

[Lucy64]

I would check for a bad or burnt plug wire or bad plug. I had the same problem on my 64 and found a plug wire burnt by the header.

 

[WNH]

I would check for a bad or burnt plug wire or bad plug. I had the same problem on my 64 and found a plug wire burnt by the header.

Could also be a scared wire sending a spark, or a loose plug. Both happened to mine.