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87 560SL. 03 SL500. 10 GL450.
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12 Posts
Discussion Starter #1
Have a great 87 560SL, bought two years ago. At idle, I have begun to notice an inconsistent firing of the cylinders. Occasionally it will sound like 2 or 3 fire harder than the others, and at other times it sounds like 6-7 of the 8 have a rough sound. Not smooth and not consistent, seems to be different on different days, although recently I've noticed more of the cylinders having this trouble. Don't notice as much when driving, but I think it's happening there too.

I believe this means I'll need to change spark plugs - Can anyone confirm this analysis, and I'm correct - recommend a photo-tutorial which shows me how to do this?

Never tried changing plugs before. (This forum was very helpful when I changed my oil today, had my 14mm hex socket ready..) Any advice/counsel would be greatly appreciated. I love this car. Has 186 thousand on it and I would like to keep it for the rest of my life...
 

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1986 560 SL
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7,354 Posts
Aside from spark plugs, there isn't much to "tune up" on a 560.
Idle speed and timing are not adjustable.

Certainly new plugs and maybe wires are in order, if only to eliminate those easy items as the culprit for the PO's problem.

As to a photo-tutorial on how to change plugs, maybe UTube has some generic video. The 107 really isn't any different from other cars. The rear plugs are a bit awkward to get at, but that's so with most V8s. Just be careful pulling off the rubber boots and be sure to start the new plugs by hand so as not to cross thread them.

Give it a go. It's probably the easiest DIY job you'll tackle.
 

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It Is What It Is, Dude
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22,841 Posts
As to a photo-tutorial on how to change plugs, maybe UTube has some generic video. The 107 really isn't any different from other cars. The rear plugs are a bit awkward to get at, but that's so with most V8s. Just be careful pulling off the rubber boots and be sure to start the new plugs by hand so as not to cross thread them.

All that, and never pull the plugs from an aluminum head when the engine is warm.

Always cold.

And install them with a small amount of anti-seize compound.
 

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Registered
87 560SL. 03 SL500. 10 GL450.
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12 Posts
Discussion Starter #8
thanks

Many thanks for the words. No idea when the last plugs were in, but will make an attempt with the Bosch Gold non-resistor type. Just don't want to mess up the air cleaner or other items in the process. Thanks for the help.
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,345 Posts
Take the air cleaner housing off and put a rag in the hole.
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
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32,345 Posts
Before you pull the plugs remove the distributor cap. Inspect it and the rotor. Easy to do.
 

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Registered
87 560SL. 03 SL500. 10 GL450.
Joined
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12 Posts
Discussion Starter #11
Had ignition system completely checked out. Installed new plugs which helped, but not completely - then a can of Chevron Techron in the gas tank, followed by a long drive down the interstate completely eliminated the mis-firing problem. Car runs flawlessly now - cannot believe this is a 23 year old 560SL with 186k. Have tried other fuel additives with no luck - A bottle of Techron seems to be money well spent, based on what I just experienced.
 
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