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.

[ThinAir]

Since you were running a non-stock, adjusted, MPS - are you running the stock CHT?

On my '73 I found that I could run both the 037 and 043 MPS units with the stock 017 CHT, but after I changed to a new 012 CHT the 043 MPS would idle evenly for a few moments, then the engine would die.

See this thread for the long story. I may have had MPS issues (or MPS / spark plug placement issues), but ultimately it turned out to be something in my distributor.

[thompson-mfr]

Since you were running a non-stock, adjusted, MPS - are you running the stock CHT?

On my '73 I found that I could run both the 037 and 043 MPS units with the stock 017 CHT, but after I changed to a new 012 CHT the 043 MPS would idle evenly for a few moments, then the engine would die.

See this thread for the long story. I may have had MPS issues (or MPS / spark plug placement issues), but ultimately it turned out to be something in my distributor.

I am running a stock 2.0l CHT. I had to adjust the 019 T4 unit to get it to run right (last one). Was running great with really good power.

This was a good suggestion. Maybe I will replace the CHT to be sure.

I just put another T4 MPS (PO had a box of them) and adjusted it to run good(currently).