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I know why my car was idling like crap...

691 Views 9 Replies 5 Participants Last post by  roncallo
Decided to take my own advice and put a set of NGK BP5ES in die Weisse Lady. Discovered two problems with the old plugs. The first was that they were Bosch WR9DC+ resistor plugs, and the wires were still Bosch resistor wires. Not sure how much difference that makes.

Here's the second problem:

Spark plug Auto part Automotive ignition part Automotive engine part Fastener

The numbers are the cylinder they came out of.

#8 isn't supposed to look like that, is it? Not only that, but what you can't see from the picture is that the gap is a lot narrower than on the rest. I didn't try using the gap tool on it, but it looks like it's half the width of the others.

The car runs and idles a lot more smoothly now. The big question is: where'd all that crap on #8 come from?
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I've been trying to make my 1973 280se 4.5 m117 run as well as possible, assuring EVERYTHING has been done before replacing the valve stem seals that I know I need to replace. I have pulled, replaced, and pulled again the spark plugs. #4 and #8 are the most oily. I'm not sure why, but I'm guessing that those two have the worst valve stem seals. Another possible factor, (especially since I got ~10% lower compression numbers on the #8 cylinder than all others) may be that the rear cylinders are farther from the oil pump than all the other cylinders. I wonder if I could have a worn ring on that #8.

My only concern is the large puff or stream of oil smoke I make when I press the gas, let up on the gas, or start the car. :D

That's just my scenario and my issue. Yours may be different, but as was said above, changing the spark plugs every once in a while isn't as difficult as other solutions.

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