Hi guys!

First post here.
We have this mustang for 26 years now, and it has always ran fine.
We've had to replace some things over the years, plugs,wires,.. but it has always been in good condition.
Went on the first trip in a year a few days ago and it started to really really run bad. Sounds like it's only running on 4 cilinders, won't idle.
First thought was a blocked carb but that wasn't the problem ( checked with a different carb, same problem)
Changed the coil and condenser and reset the points => no change.

A bit puzzled here. It has some fresh fuel as well. Can't imagine its something catastrophal either ? Any ideas? Only thing that wasn't changed for a new part is the points, but can't imagine those would go bad in this way?

Thanks in advance

 

First thing I would do next is pull the plugs and look them over; see if any are fouled or indicate another issue. Also check vacuum hoses for failures.

 

and while you have the plugs out do a compression check.