Last October I bought this 85 Red GT convertible with a little under 36k. It has an all stock 5.0 with the 4180 carb and 5 spd. It seemed to run fine when I got it home, then put away for the winter, then started up this spring. Again, seemed to run fine but I noticed some backfiring. Next time I tried to start, it choked and coughed and barely held idle. Definitely not roadworthy.
I started pouring over previous posted threads to see what was shared on similar issues. Recommendations ranged from replacing the EGR valve to the power valve in the carb. So I did both. I replaced the original 2-stage PV with the single stage that comes in the carb rebuild kit. The engine ran much better so I thought I had addressed the issue. Not so lucky.
Once I drove it for about 15-20 minutes, I could begin to detect a missing either at speed or accelerating. Then when stopped, it would idle at about 1k to 1200, then drop to almost a stall, sometimes recover, sometimes stall completely. My next suspect was the ignition system.
I've now replaced distributor, coil, spark plugs and wires, and the ignition module; Motorcraft where possible; the dizzy from LMR. While it does run somewhat better--accelerates well, holds speed, etc.--I still have the idle-drop issues and an occasional misfire on acceleration (e.g., taking a right turn and starting up from 2nd gear).
Any advice or guidance would be appreciated. Just not sure where next to turn. Thanks!
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