97 Aerostar 4.0. Half what thru my 300 mile trip, I hear hissing like compressed air........ Loss of power shaking. Nursed it to walmart supercenter best non gas station. Lights supplies oil etc. I see defense sensor hoses burnt thru (compressed air sound) and back of dpfe mounting melted with a hole the size of a pinky. Tried using a filler piece and rtv sealant ......no luck. I'm leaving now to uhaul it home. Here's my thinking.
Cats may be blocked. Forcing exhaust under pressure into dpfe. Burnt dpf burnt hoses and then intake manifold. Had no vac for the booster while slowing down.happened at 70mph pulled over asap then nursed it to Walmart. I miss the metal intakes.

 

1 CAT.

Or plugged muffler from internal corrosion then collapse of internals blocking outlet.

Has the motor been running rough rich? Exhaust smell like old stinkpot rich gas?

The replacement upgrade DPFE sensors are all plastic, no internal corrosion and they melt instead of the plenum

 

It's still on its original injectors now at 487k. I will do an exhaust back pressure test tomorrow. I did notice that it would drop out of overdrive on slight inclines and lose vac to the ac registers. What I think happened as I'm driving at 75mph 2hrs iinto the drive that due to partially blocked cats, the back pressure forces exhaust gases up the 2 silicon dpfe hoses ( which one was burnt thru) and melted the plastic dpfe sensor (4 years old) the metal in the center of the dpfe sensor got so hot and in conjunction is it possible that the pressure could have forced the egr valve off its seat adding to the heat build up. The burnt hole is behind where the dpfe sensor mounts and where the egr tube slips into the manifold.

 

I pulled the intake manifold. Hole was bigger than I had seen while it was on. I went to get another at the local pick a part. They only had a 94 4.0 intake metal type. Took a chance on that. Used the 97 throttle body. The cats were clogged badly. I cleaned them out. Then took it for a run. Never ran better. 94 didn't have egr so left it of. Connected new dpfe . All ok.