'87 300TD manifold sensor craziness

[cantabridgian]

Hi All,

This is way beyond my skills, I thank you in advance for your input. My '87 300TD (#14 head, yes!) runs well except for one big problem - lately when on the interstate (for example) and I push down hard on the accelerator, the vehicle won't really accelerate - seems like it wants to, then backs off, then feeds more diesel, than backs off, over and over again until I back off the gas pedal. Here's the interesting part: if I yank the manifold sensor wire from the manifold and leave it dangling, the car accelerates normally, even quickly. Sometimes a little white cloud of smoke (even when warm) from tailpipe when flooring it at, say, 75 mph (kickdown switch triggers downshift, cue small amount of white smoke and the car accelerates quickly). When I reconnect the manifold sensor wire - problem resumes. What???

Everything else largely normal, all filters new, did a diesel purge a while back, getting solid 30mpg @ 75 mph on the interstate, probably about 23-26 mpg around town depending.

I do occasionally notice the dome light doing a 2-flicker, 1-flicker (on the seatbelt warning light above), repeat, while my (new) glow plugs are heating, but apart from that I don't notice anything out of the ordinary.

Thanks!

Josh