2000 Focus strange behavior

[brother rat]

Driving our Focus wagon down the freeway at 75 mph, sudden rattling sound and no power. The rattling was pretty quiet, like I had a piece of plastic or something stuck in the grill flapping in the wind (I actually thought the car next to me had the rattling sound). As the car slowed to a stop, the engine would rev slightly as I pressed the gas pedal, but no acceleration. Stopped the car and the engine died. Smelled like sulfur (sorta like fireworks). Tried restarting and the engine wouldn't idle (continued to hear mild rattling and smell sulfur). I had my wife sit in the driver's seat and crank the engine and keep the rpm up so I could look for the source of the noise and smell and found nothing. Suddenly, the engine started again, idled normally and I drove 120 miles home no problem.
Our Focus has the SPI engine. The original motor dropped a valve/threw a rod and was replaced about 100k miles ago. At first, I thought the same thing happened again or maybe threw the timing belt.
Now the only things that come to mind are either a fuel delivery issue (pump/filter) or a transmission issue (some random glitch in the electronic control). The funny thing is that the CEL never came on. Any thoughts?

 

[martin]

Only thing I can think of is that the cat fell apart internally, causing a blockage, then broke up further and allowed gasses to pass again.

 

[adsm08]

I am thinking along the same lines as Martin. Cat collapsed, and then started popping pieces out into the system letting exhaust pass again.

It accounts for the rattle, the stall, the poor idle, and the sulfur smell. The oddest thing about a collapsed cat is that they don't always set cat efficiency codes.

 

[brother rat]

Thanks for the input fellas.
I'll look into it.

 

[brother rat]

Mechanic says that one of the PCV hoses was collapsed. He replaced the lines and the valve.
I guess I'll keep an eye out in case it happens again and we'll see if it passes smog check next year.