"1.7 lost power, won't idle"-Now Runs! But..., without MPS connected....What the?? Options

[porschefool]

Hey gang,
'72 1.7 runs fine now, all I had to do was pull the vac line from the MPS. Why the hell would THAT do it?
Can I live without it?
Doesn't make sense..

Thanks to all who gave input!

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[McMark]

If it's running fine when the MPS is not plugged in at idle then something is way off. It shouldn't idle very well. Thinking about it logically it seems that your car is running very lean and by pulling the MPS hose you make the computer think it's at full throttle and pump in more gas. I'd pull your injectors and see if they're spraying nice.

Unbolt both injectors on one side and pull them up and away. Unplug the coil (black wire on the + side) and unplug the connector from one of the injectors. Place a towel or rag under the injectors and have a friend crank the engine. You should see a fine even cone spray from the injector that is still plugged in. Replace the plug on the unplugged injector and pull the plug on the other one. Repeat. Then do the other side. Be careful because gas is explosive. Use your brain.

If the gas comes out in a stream you have dirty injectors. It should be a nice strong fan spray. If all the injectors have the same bad spray pattern it could be that your fuel pressure is too low to get a good pattern. Check the fuel pressure and then test the injectors again.

Make sure not to lose the rubber seals on the ends of the injectors when you pull them. They must be there or you will add more problems.

As a test, you might try pulling the temp sensor connection as well. It's a two wire connector that is plugged into a sensor on the air plenum body. Pulling that connection should enrich the mixture and let you see if you really are running lean.