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?

[lsintampa]

I chased a surge for over a year on my 2L (1975). Replaced all hoses, had MPS rebuilt, replaced TPS board, adjusted ECU knob, pretty much went through the entire gambit.

Finally took it to a shop who's owner started working at a Porsche dealership back in 1974 and he's only been working on Porsche's since. Mostly the vintage cars.

He found at least two leaks in my plenum using a smoke test. It's a machine that uses oil to make smoke which is blown into the air box (engine off) after sealing off any potential places for the smoke to escape.

Both leaks were pinholes in the plenum - and both on the bottom. Very hard to get to with spray.

IDK, I tried spraying all about prior to the smoke test, never once did I pick up any sign of leaks.

I will only add that I had been very skeptical of a "leak" for over a year. I was sure I didn't have a leak, only to find out that indeed there was a leak.

So bottom line - is most likely you have a leak. I'd suggest a smoke test to rule out any leaks - or more likely - find out where your leak is.