Thread: Strange cyclic running to rough-running (up to reduced engine power mode)

Car was running fine, I came out on the road to beat upcoming traffic, hit a small chuck hole (would not have thought anything of it), felt a loss of power, car went to reduced power mode, got to parking lot, stalled.

Stared it after a few times, on my way, went to loss of power. Continued driving to get home, stalled, tons of misfires (registered on AeroForce Interceptor scan gauge, no DTCs), eventually drained battery.

Got it towed home, charged battery, started it, runs, then runs rough (like a vacuum tube is off or wild camshaft pulsating), returns to running "good", returns to the cycle again. Sometimes it almost stalls, then gasps and runs "OK".

I looked for disconnected vacuum lines or electrical connections - nothing obvious jumping out (no DTCs registering except misfires)


I'm somewhat stumped and have never seen this cyclic action. Posting this for any ideas before I begin looking at it tomorrow. The bump in the road seemed awfully coincidental. Thanks for looking.

Yep, it was a vacuum hose - the one below the S/C snorkel (since when I replaced fittings and the tee fitting here was not available, I used a universal part. Its size is a bit larger than the port at the manifold which lead to slightly oversized vacuum tubing. I recall knowing it wasn't the tightest fit, so I found some other tubing and used a spring-ring. It appears to be good, and I might even find some intermittent misfires go away. Whew.

Thanks for reading, FordMan77.