Author Topic: spark plugs defective after ±3000 km ?  (Read 5263 times)

Ziggy

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spark plugs defective after ±3000 km ?
« on: September 18, 2008, 12:43:41 »
I fixed a very weird problem today. The engine has been running perfectly but suddenly began misfiring and hesitating when accelerating from idle. Also sometimes it would idle perfectly for a while, the next time it could barely idle at all. I changed ignition wires, coil, checked everything but could find nothing (everything is brand new...)
It was an ignition problem for sure, so eventually I decided to change the spark plugs.
That seemed to be the problem, but...
The spark plugs (ngk bp7es) were only about 3 months old[:0] the gap had not changed, the color was right and they just look new.
What could be the problem ? I am thinking it must be something with the internal resistance of the spark plugs?
 :?:
« Last Edit: September 18, 2008, 12:44:47 by Ziggy »

Richard Madison

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Re: spark plugs defective after ±3000 km ?
« Reply #1 on: September 18, 2008, 17:40:56 »
I'm no techie but these are fairly high compression engines and driving moderately can result in fouling...rough idle, rough acceleration, etc.

I'm in New York City and do a fair amount of slow driving.

A run at moderately high rpm for 5 or 10 minutes might clean up the gunk.

When Ole Beige is getting rough, I take her out on a highway at about 50 mph but leave it in 3rd gear so it revs near 4000 rpm for a while...does wonders. Maybe this is all you need???

Richard M, NYC
« Last Edit: September 18, 2008, 17:41:19 by 280SL71 »
1969 280 SL, Tunis Beige, Euro Model (Italy).

Ziggy

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Re: spark plugs defective after ±3000 km ?
« Reply #2 on: September 19, 2008, 10:01:56 »
They weren't fouled. I decreased the gap to about 0,7mm and put them back in, there was still some misfiring now and then, but a lot less. Perhaps it has something to do with this hotter cam: http://index.php?topic=9274

Ulfi

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Re: spark plugs defective after ±3000 km ?
« Reply #3 on: September 22, 2008, 06:46:07 »
A little "Italian Tuning" also does the trick for me - and it's great fun too!!

hill

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Re: spark plugs defective after ±3000 km ?
« Reply #4 on: September 23, 2008, 10:44:12 »
Aren't  BP7es the coldest plug in that range?

ja17

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Re: spark plugs defective after ±3000 km ?
« Reply #5 on: October 05, 2008, 07:57:01 »
Hello,

Yes, Darryl is correct, in most cases we are using BP5es or BP6es are used in these engines.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback