I just bought a 1994 Park Ave. in beautiful condition. I got it kind of cheap as it came with an issue: it likes to stall and die when the RPM drops too low. I’ll try to describe the problem as accurately as possible.

When you start it, it runs fine for a few minutes. Then the RPM starts swaying up and down and it eventually dies. The symptom is the same regardless if the engine is hot and cold. When it has died it starts right back up again and runs for a few minutes before it starts again. Each sway of the RPM is accompanied by a whiff of smoke and smell of gasoline from the exhaust, like it gets too much fuel. If the RPM is kept above 1200 it will run fine. I drove it home on the highway (around 120 miles) after I bought it, and made sure the RPM never dropped below 1200.

This is what the previous owner did in trying to eliminate the fault:
Cleaned the MAF, replaced plugs, wires and ECM, replaced the TPS, replaced the fuel pressure regulator, replaced the EGR valve, replaced the Idle Control Valve, replaced a lot of the vacuum tubes. Nothing of the above fixed it.

I didn’t have much time to tinker with it yesterday but tried and noticed this: Disconnected the MAF - this increased the sway of RPM, but it didn’t seem so inclined on stalling.

Sprayed starter gas around the intake manifold - no result, so I don’t think that’* where a potential leak is.

While doing the above I noticed that the problem seemed to get worse whenever the clutch for the AC engaged. I took it for a test drive with the HVAC system switched completely off and it seemed a little better, but still stalled on me a couple of times as the RPM dropped.

Any ideas of where I can check for a vacuum leak? I think the previous owner changed most of the hoses that are immediately visible when you look down at the engine.

Thanks! And if you made it this far; sorry for a long post

Throw a fuel pressure gauge on it.

I don’t have one unfortunately, but I think you’re on to something. It runs almost perfectly smooth when I create a small vacuum leak by pulling the line to the cruise control. With no vacuum leak it behaves as in the video below. I think it’* getting too much fuel.

The fuel pressure regulator is brand new.

Fixed it! It runs perfectly now.

It was a bad ground connection for the O2 sensor.

Cool, glad you got it figured out!

Thanks for letting us know what fixed it!