Surging and Unsettled Idel after MPS Rebuild, '74 2.0L D-Jet Options

[914four]

Running down a bucking issue and found my MPS to be leaking. After rebuilding the MPS and verifying a good seal, everything went back together okay. When I started the car, the engine surged up and down and would not idle.

The electrical connector socket on the MPS does not appear to be keyed and using the diagram below from Clay's D-Jet troubleshooting guide it seems I may have plugged in the MPS wire incorrectly. I ohmed the wires from the ECU connector to the MPS socket and made sure the wires are in the order shown in the diagram.

The wires look to be looping back from terminal 7 to 15 and 8 to 10 so that the socket could be plugged in either way and work correctly. Could plugging in the MPS wires incorrectly have damaged the ECU? If not, what should I be looking for that would cause the surging and lack of idle?

[R Shaff]

I know this is an old thread, but for anyone who wonders about intake leaks, the cigar smoke test is cheap, easy, and can be done at home. Light the cigar and take long slow draws on it to let the smoke collect in your mouth, then blow the smoke from your mouth into the intake. On this car (mine's a '72 1.7L), I disconnect the PCV hose and blow into it. Then once the intake has plenty of smoke in it, I blow harder to see if the smoke comes out anyplace but the air cleaner.

[Rand]

I know this is an old thread, but for anyone who wonders about intake leaks, the cigar smoke test is cheap, easy, and can be done at home. Light the cigar and take long slow draws on it to let the smoke collect in your mouth, then blow the smoke from your mouth into the intake. On this car (mine's a '72 1.7L), I disconnect the PCV hose and blow into it. Then once the intake has plenty of smoke in it, I blow harder to see if the smoke comes out anyplace but the air cleaner.

Curious. You'd have to cap the throttle body air tight, or it would just come out there. Seems like it would need to resist some pressure. Did you seal it or just use your palm or what? Is this a theory, or has it actually helped you find an intake leak? Interesting idea.