Sudden rough idle??? Something to check - 560SEL
 

Last Thursday night, I was preparing for a run to Laughlin, NV for a 3-day weekend of fun, sun and gambling. Ran to the bank to hit the ATM and upon starting the car I heard a "pop" with immediate rough idle. I also noticed that the economy gauge was at the halfway point at idle, lower with the A/C on. I made it home and did a cursory check with nothing appearing out of the ordinary.

Not having the time to find the problem and not wanting to drive the 560 with it's rough running, I took the Suburban and enjoyed the weekend.

As soon as I got home this afternoon, I popped the hood on the 560 and starting troubleshooting. First stop was to check the vacuum at the EZL, only 10 inches HG at idle. Next stop was the check valve to the air pump (engine warm, pump off) no vacuum at either leg, hmmm....

Popped the air cleaner assembly and the problem was staring me in the face. The 90* elbow, where the vacuum line attaches to the intake (pass side of the throttle body), was laying off the stub. Reattaching the fitting returned everything to normal. I guess I need a new elbow, the old one is a loose fit.

Now to figure why it popped off in the first palce, or try to recreate the event.

Just thought I'd post this for other who suddenly encounter a rough idle and poor running after a short drive/stop/start scenario.

Thanks Mike!! Good info as usual. :D

Our 560 is taking a few weeks off, since wifey had some minor surgery and can't drive, so I'm chauffering her around in the '69 Fleetwood. :rolleyes: ;)

Mike,

My older 420 did the same exact thing one time!! I would hear a pop and then it idled like a muscle car. sure enough, that same elbo piece blew off.

Good advice to anyone with this car.