When I start my 1972 1.7L, the idle immediately goes to 4,000 rpm. The only thing I've done recently is replace all the fuel lines down under where the fuel pump is.

All vacuum hoses appear to be connected. I did not remove the air cleaner to check anything under there, but I did tug on them and nothing came loose.

It happened like this: stopped the car to open the garage. As soon as I restarted it, it went to 4,000 rpm. I thought I heard a noise in the car (like something came loose or broke or something, but I'm not sure).

A friend of mine told me it might be something down around the clutch and gas pedal assembly. I could not find any crossed wires or anything. I do not have a pedal board, by the way. Not sure if that matters, but I mention it in case it does.

Any ideas what could be causing this?

That can cause all sorts of problems since you don't have any pedal stops without the board.

You could have snapped off the pelvis that for one of the cables, overextended a cable, broke the clutch tube and a few more possibilities.

My guess would be something broke around the pedal cluster and got your accelerator cable stuck.

You may have twisted the accelerator cable around the clutch cable.

Check your engine bay, make sure the throttle body is closed.
Start the car in neutral without depressing the clutch.
If it does not idle super high, gently press the clutch pedal and see if it acts like the gas pedal....making the engine go faster.

More than a few of us have done this.

Rich

Appearances can be deceiving. Vacuum leaks can come from the most inconspicuous places, and cause a high idle like you're experiencing. Go through every vacuum hose connection and make sure they're all tight. It would take a significant vacuum leak to get your idle that high.

My old '72 car didn't have a pedal board either. As long as you don't lead-foot the pedals like an elephant you should be ok. But maybe remove the air filter and the intake air elbow and see if you can see if the butterfly valve is stuck open.

If it turns out to not be the cable issue as mentioned, you might want to double check your timing. I have had similar issues when the timing was not set properly. The distributor advance could be sticking as well. All kinds of spots for issues to present themselves with D-Jet. Fortunately, with enough time and determination, you can figure it out. Good luck.

Vacuum hose on the oil breather.

4,000 RPM is one heck of a vacuum leak. Probably one of the larger (~13mm) hoses has been knocked off of the manifold. Either that, or the throttle is stuck open a fair bit.

--DD

I found it! It was the vacuum hose going from the oil breather to the plenum. Not sure how it got knocked off, but it's just a press fit and seems a bit loose. Maybe I should put a fuel hose clamp on it?

The sound I heard must have been the hose popping off the connection.

Thanks to all for your advice.

Here's an image: The air cleaner has been removed for your viewing pleasure. The hose goes from the "L" connector to the oil breather.

Click to view attachment

A 1.7 has a vacum hose from the breather tower to the plenum¿

Yep! At least mine does.

Oil breather to plenum would be correct