Chrysler Repair: 91 voyager engine stutters, vacum leaks, electronic speedo

Question
i have 91   ply voyager 3.0 auto that I changed rear head on. it runs fine sometimes but eventualy it stutters and bogs while driving also electronic speedo is erratic at these times. no codes, have had it hooked up to diag machine twice by 2 shops. have verified all grounds and electric connections. no vacum leaks, have changed, plugs, dist. cap, tps,speed sensor, coil, distributer, coil to dist. wire, ecm, fuel filter,timing  belt seemed fine, when i changed ecm (used) the problem reappeard but speedo doesn't work at all now. if you can solve this one you're a wizard.  

Answer
Hi Jim,
I would work with the correlation of the speedo erratic/dead and the stuttering/bogging. Although you replaced the speedo sensor there are two other possibilities:
First the wiring from the sensor to the ecm. You could verify that you have a good connection between the white/orange wire at its disconnect plug and pin 47 of ecm plug, and the black/light blue and pin 4. To locate the pins hold the 60 way plug horizontally with the short tab up, pins facing you. Left end of upper row is #1, then going left to right end which is #20, then cycle back, etc. Try an ohmmeter between those pin assignments and the disconnect plug, and shake the harness for possible flakey connection along the length, since both wires go thru a 10-pin disconnect (gray in color) located behind the battery which might also have a flakey connection.
The other, though it is unlikely, is that the sender gear meshing with the right half shaft is flakey, so check the sender gear and also if nothing else works try to verify that you get 8-pulses per turn of the right front wheel with an ohmmeter placed across the output pins of the sender. It is not likely, but the very last possibility is that the splines on the halfshaft are damaged so that it doesn't drive the speedo sender reliably. But that is a hassle to remove and find out. If you do, always remove the speedo sender first before pulling out the half shaft, otherwise you damage the gear on the sender. Because the ecm needs the speedo sender data for proper operation of the engine, I would try to resolve that matter before going any further.
Roland