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  #1  
Old 06-16-2004, 02:53 PM
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Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
Lumpy Idle 380SL - The Saga Continues

From the day my 380SL arrived in my driveway (on a flatbed), it has had a rich and lumpy idle. Until last night, when HBofinger came over and re-soldered the idle control unit, it also had a surging, rich, and lumpy idle.

It does not seem to be a specific cylinder. I "cracked" three injector lines (one at a time) on the FD, with barely a change in idle. I also disconnected a couple of plug wires with not much change.

There were small bubbles in the gas that came out of the FD.

The spark was very strong.

Pulled a plug and it was very sooty.

Leaning the mixture made the idle worse.

On/off ratio fluctuating around 52-53%

In the last 6 months:

FD, injectors/seals, idle valve, all air hoses replaced. Idle control unit re-soldered. Intake manifold resealed.

Fuel flow and pressures (system and working) were checked about three months ago, and were very close to spec. Starting and running otherwise good.

This is a euro engine (compression and cams) with the US injection and controls.

Makes no sense!

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #2  
Old 06-16-2004, 05:20 PM
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Join Date: Mar 2003
Location: Montana
Posts: 65
FWIW

Chuck, when I had high idle hell, surging, quitting, you name it out of the many things I did I re-soldered my ICM, then bought a rebuilt, then bought a new one and it did clear up some issues. A new one may solve some of your problems. I also found the little sockets in the plug in for the ICM to be loose and took that plugin apart and squeezed the sockets together a tiny bit and it solved some intermittent issues for me. You can diagnose this by moving the icm plug in wire bundle around that goes from the icm to under the brake master cylinder and booster. If there is change you know you have some loose sockets on that plug.

Am not sure if you have that accelerator enrichment switch we discussed on another thread -- I am sure if you do you have already shorted across the plugin to see if that helped your idle.

I had to also plug the top vent on the Warmup comp.

It seems in my readings that a throttle switch is also a chief culprit in idle problems.

Not sure if I have any other ideas.

In my troubleshooting I sure wish there were a way to test for vacuum leaks that was quick. Seems to be many connectors and feet of vacuum under there and I don't know how anyone could troubleshoot the vacuum systemwide.

Don
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1984 500 SEL [131K]-
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  #3  
Old 06-17-2004, 10:28 AM
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Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
Problem Sort of Solved

Ran the car yesterday and the problem grew worse by the minute. I decided to take a look at the plugs, and started removing the right side. Discovered (blush) that the throttle switch wire was against an exhaust manifold and had fried to the point where one of the wires was grounding. Fixed that, and drove the car a few miles. Idle is now somewhat less lumpy and smells less rich, but still poor.

The on/off ratio is fluttering around 52%.

The voltage to the ICV is between 2.5 and 3 volts at idle.

Will continue checking and report.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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