Looks like the switch locks out the EGR system at low engine temperatures.  Can't tell if the switch is normally open or normally closed though.  You didn't say what temperature the engine was at.

Emission Control (EC) chapter.

Ok so while getting that switch sorted helped, we MIGHT have found the final culprit which is the AFM.

We went through the below procedure and only got ohm readings on the upper third of the wiper band (upper being where the pedal is more mashed to the floor) on the AFM's circuit board.  We even tried pressing the wiper down onto the black/carbon stripe to see if maybe it was bent up and still didn't get any readings from it until the wiper got up into the top third.  We sanded the wiper arm contact in case it was corroded but this didn't help.  I'm guessing that isn't normal and there should be readings on the multimeter for the duration of travel, correct?:

 This is page EF-30

Edited August 28, 20222 yr by chaseincats

are you using a auto ranging multimeter?

You have the wrong picture with the test method.  The picture is for a single resistance measurement, not vane movement.

Here is the correct picture.  Terminals 7 and 8.  And you're looking for smoothness of the voltage reading, not resistance.  Page EF-51 and 52.

p.s. you should not sand the carbon trace.  It's not very thick, you could ruin it.

1 minute ago, Zed Head said:

You have the wrong picture with the test method.  The picture is for a single resistance measurement, not vane movement.

Here is the correct picture.  Terminals 7 and 8.  And you're looking for smoothness of the voltage reading, not resistance.  Page EF-51 and 52.

p.s. you should not sand the carbon trace.  It's not very thick, you could ruin it.

My FSM only goes up to page EF48 (1978).  Are you looking at a ZX book?  Sorry, I meant to say we sanded the wiper contact - we put sand paper between the carbon trace and wiper with the soft side sitting on the carbon.

1 hour ago, Dave WM said:

are you using a auto ranging multimeter?

We ended up slightly bending the main metal arm that connects to the circuit board contact which touches the wiper arm's single point towards the top and then we got a reading.  The car still stumbles on acceleration however.  After all this I just advised my friend to take the car to a shop and be done with it.

12 minutes ago, chaseincats said:

My FSM only goes up to page EF48 (1978).  Are you looking at a ZX book?

You posted in the 1975 "strange intake noise" thread.  I used the 1975 FSM.

Still - wrong test method.  There is no method for measuring resistance across the vane sweep.

4 minutes ago, Zed Head said:

You posted in the 1975 "strange intake noise" thread.  I used the 1975 FSM.

Still - wrong test method.  There is no method for measuring resistance across the vane sweep.

Sorry, you're absolutely right - opened the '75 manual for his car and found it there.  I'll relay the message thanks Zed