1999 Ranger XLT, 4L. 4WD. My engine appears to be missing and intermittently jerks. Starts fine. No check engine light, no codes on a scan, however they can see up to 3,000 misses on #4 cylinder in the history. New plugs, new coil pack, newer plug wires. They ran c-foam through the gas tank and in the intake. It's unreliable. I can find no correlation such as fuel, engine temperature, throttle opening, etc. It does appear to happen under a load (on gentle hills) . Driving to town it may or may not jerk. Some days it acts up and sometimes it doesn't. Occasionally it feels like it "clears its throat", pulls strong, and quits jerking, only to start messing up again.

It would be nice to trust a vehicle for a change.

Any thoughts?
Frustrated and going broke- ggrrrrr,
Thanks...