Manifold Pressure Sensor MPS and timing, what is the effect on timing? Options

[thompson-mfr]

Ok, I will try and keep this as brief as I can.

I will pose the question before providing the background.

?? What, if any, effect does the MPS have to do with actual timing of the motor??



Now for the reason for my question.

1974 2.0L FI

My MPS (0 280 100 019 adjusted VW T4 unit) randomly stopped working properly even though electrically it checks out and holds vacuum. Maybe an aneroid cell? anyway not sure. I then started trouble shooting thinking it was points, plug wires, etc. ( I replaced to be sure) and readjusted the timing and dwel.

Right after the MPS stopped working I found a good deal on another nice '74 2.0 FI 914. It has a factory MPS correct PN 0280 100 043 and runs perfectly.

So, I thought I would swap MPS's and see if this fixed my problem. It didn't run well.

Thoughts?? I have read Pbanders a bunch of times.

I have included a picture of the new car in hopes there are others like me that like pictures. I only open threads with pictures as I cannot read good (well )just joking). Maybe other people can relate to this.

[brant]

I hope your using a wideband o2 sensor to adjust these.
I have seen with my own eye's on the sensor that you can not tune these by feel or ear. The adjustment is way to sensative.

[thompson-mfr]

I hope your using a wideband o2 sensor to adjust these.
I have seen with my own eye's on the sensor that you can not tune these by feel or ear. The adjustment is way to sensative.

No I do the guess and check method. Adjust a little then drive....adjust a little then drive. I only adjust the small inner screw. The full load stop is drilled out in the middle.

I don't have a wideband o2 sensor reader, or are you talking about taking the voltage from a single wire o2 sensor?

Please tell me how you do it. I would like to avoid buying any more expensive measuring equipment if possible.