replaced ignition coil, now car has EXTREMELY high idle

[WANT '71 280SEL]

Suddenly last week my mom's 420 wouldn't start. It was diagnosed to have a faulty ignition coil. After replacing it, the car now idles at 2000rpms cold and 2400 warm. When the car is put in gear, it chirps the tires and idles at 1000-1200 rpms. I've had the vavle covers off and have tried to start it several times with gas, carb cleaner, etc. being put into the intake. I've let it idle and driven it about 5 miles since, and it still idles really high. I thought it may have been left over carb cleaner, but that would burn off instantly, right? Can someone please offer some insight into this problem?
Thanks
David

[WANT '71 280SEL]

If I unplug the ICV, the idle goes up even more, so that seems to be working.
Thanks
David

[william rogers]

Don't see how it could be related to a new coil just replaced coil on my 500 SE. Would have codes read.........

William Rogers.......

[Chevota]

Vacuum leak maybe, or something like a tool or bent throttle bracket holding the throttle open a bit? These have all happened to me before, but mostly the vacuum leak.

[fahrgewehr2]

I'm with these guys. I don't see how an ignition component could raise idle speed, it takes air to accomplish that.

[WANT '71 280SEL]

I checked the throttle, etc. and it all is resting at idle. Would having the air box off effect it? I haven't run the car yet with the air box. The car ran great when my brother moved it 20 feet to wwash it. After that, it wouldn't start until I replaced the coil. Now that I have it running, it is idling extremely high. I've triple checked all the vacuum connections and they're all plugged in.
Thanks
David

[WANT '71 280SEL]

Wouldn't it have to be a pretty big vacuum leak to do this? A line would have to be completely disconnected for a leak this big, or I would think so.
Thanks
David

[Chevota]

I'd put the airbox back on first. Also look at the throttle valve to be sure it is actually closed. Air has got to be getting in there somehow or wouldn't be doing that.
Also, you said you washed the car then it wouldn't start. Did you get the coil, wires, plugs or distributer cap wet? I've had misfires from water in the distributer cap or water in the spark plug hole(s).

[WANT '71 280SEL]

The cap was dry, and I grounded a spark plug and got spark, it was just weak. Then a local mechanic came over and disconnected the wire on top and barely touched it to the coil. He said usually you should be able to hear it make the "pop" noise and see the spark jump, but you couldn't on ours.
Thanks
David

[WANT '71 280SEL]

Just went out and sprayed the vacuum connections under the hood, and the idle would not even budge. However, I stalled the car on purpose and I walked around to the trunk to put the air box there, and the fuel pump was running! Why would it keep running a minute or two after the car had died?
Thanks
David

[Chevota]

I imagine it depends on the car, but I would think the pump would run as long as the key was on. You said you stalled it so I'm assuming it was still on.

Hmmm, weird. What did you spray it with? On a carbureted car I spray with something flammable like carb cleaner or brake cleaner and look for an increase in idle, or a stall if the spray is not flammable. An injected car will likely try to compensate for that, but you should notice a change as it adapts. 95% of my experience is with carbs so hopefully someone else will chime in with some more answers.
That idle is pretty high though so the leak is large and should’ve been easy to find if it was on the outside. Did you look at the throttle blade to see if it’s closing?

[WANT '71 280SEL]

The large air flap is closed with the car off. However, with the car on, it's open about 1/8-1/4 inch, which I believe is where it is suppose to be.
Thanks
David

[Chevota]

If we're talking about the same part, then I think that's your problem. At idle the opening should be barely visable, just slightly cracked open.

But the car's not just at idle, it's turning at 2400 rpm's when it's just "idling". It closes completely when the car is off. If I push it open too much further, it stalls the car. That's what happened when I heard the fuel pump. I thought the pump would shut off? Becasue even when the key is turned to on, the pump runs for a couple seconds to pressurize then shuts off.
Thanks
David

[Chevota]

WANT '71 280SEL and Tim's__Benz are one and the same?

I'm guessing you're looking at and pushing on the air flow meter. Kinda spongy and when you push it down the engine dies? If so, it’s partially open because the throttle blade beneath it is partially open as well. The throttle blade controls the amount of air allowed in, the air flow flap is measuring how much air is flowing by. If you push it open, it thinks air is causing it and it will dump more fuel in to match. If the air isn’t really there because you fooled it, then it chokes itself out on fuel. With the engine off, gently push the airflow flap down and you should be able to see the throttle blade. I bet it’s stuck slightly open… At least I hope so, because I can't think of what else it could be.