Loud ticking... but it still runs (albeit with little power)

[randyw]

Pulled out of the garage last night and got about 50 feet when all of a sudden a loud ticking sound began. Pulled over and raised the hood, nothing obvious. Put it in reverse and she limped home. Very little power but she still moves. Any ideas? I've been reading a lot here looking for ideas but thought I'd go ahead and post this while I continue to research.
Thanks