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'm sorry I was talking about a wideband 02 sensor
perhaps there is someone in Oregon that will loan one to you or help out for 30 minutes and the price of a beer

On the wideband, I could see where an 8th turn of the screw was the difference between way too rich and way too lean
its a really really sensitive adjustment, and there are 2 seperate adjusments (2 screws)

brant

[thompson-mfr]

I'm sorry I was talking about a wideband 02 sensor
perhaps there is someone in Oregon that will loan one to you or help out for 30 minutes and the price of a beer

On the wideband, I could see where an 8th turn of the screw was the difference between way too rich and way too lean
its a really really sensitive adjustment, and there are 2 seperate adjusments (2 screws)

brant

yeah, I have attempted to adjust the 019 T4 MPS the same as the good 043 MPS with an LCR meter and it cannot match. The internals of the T4 MPS must be a little different. I have heard this from other sources.

Do you use an in cockpit one or a meter style. Maybe I need to breakdown and spend the $$$. I have seen them for $170 and then the cost of an o2 sensor. Does this seem right?