This will be I am sure the first of many questions I will asking, being it that I have now bought my first gasoline Benz. My other 2 cars are diesels. I have ordered new sparkplugs for my newly acquired '83 380SL. Do these plugs come pre-gapped(Bosch)? If not, what is the gap setting? I don't have any maintenance manuals on this engine just yet, so any tech help I can get to sort this car out would be greatly appreciated. Presently the idle on this engine is rough, in that it "lops", if you know what I mean. I removed one of the plugs and the gap was huge. At least more that I would expect. My past experience with German gas engines, tells me the gap should be something like .23.
Anyways, any help with learning about these engines, tech specs and such would be appreciated.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Spark plug gap should be .8mm or .32in. While you are in there replace the cap and rotor, plug wires and clean out the IAC motor. Did a world of difference with my 420SEL.

Thanks for the specs. Do the plugs come pre-gapped? I don't even think I have a gapping tool anymore. The wire set that is on the engine now is Bosch, some oxidation on the plug connectors, though inside appear to be fine, no corrosion. Is there a way to check the wires to see if they are still good, other than an obvious break? What is an IAC motor?

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Well I measured the gap of the plugs and they all were larger than 1.27 mm. My gapping tool doesn't measure down to as low as .8, but obviously 1.27 is greater than that. I have a set of feeler gauges but the largest they go is .655 mm.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

For the gapping on these plugs, .8mm is the correct gap? I just realized that's just a hair bigger than a .7mm pencil lead, which is small in it's self. I only mention pencil lead because that is the only thing I know of that is measured that small. So the gap is supposed to be that tight? Short of spending $140 on a CD factory manual, is there a source for specs on these engines/cars?

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

I just did my plugs, dist cap and rotor. I too had hard time finding gap for plugs but finally found it on a service cd. It is .032, and the bosch plugs seemed to be gapped already at this as I checked with my feeler gauge.

__________________
95 E420 ( 76K) SOLD
85 380SE(125k)
95 SL500(72k)

That's 32 thousands of inch

__________________
95 E420 ( 76K) SOLD
85 380SE(125k)
95 SL500(72k)

Well I got the plugs and I also bought a proper gapping tool that measures down to .20 inches. The plugs that came out were up near .50 + inches. I had to adjust the new plugs just a little, put them in and the idle was nice and smooth. I haven't replaced the cap and rotor. Now it's been so long since I have had a car with a cap and rotor, what again is the sign that the cap needs replacing? As well as the rotor?

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

The cap should have no burned contacts on it or carbon tracking. The rotor itself should be clean and not burned away. You can try cleaning the contacts but if they are badly burned you will increase the spark gap inside and lower your spark at the plugs. Wires should be changed especially if they have not been done for years. The insulation breaks down and if you run the engine at night you will see arcing from the wires to the block/body at several spots along the wires. The IAC (Idle Air Control) is mounted right in front of the Air cleaner next to the thermostat. It regulates the idle speed by bypassing the closed throttle valve and letting in air past it. It gets clogged up with carbon deposits and can stick open or closed. Any good carb cleaner will do the job. Ebay is a great source for ignition parts.