I have been tinkering with an intermittent stumbling problem with my 86 420SEL for several months. I finally called a tech at the dealer, who had some interesting ideas for checking it out...I had been looking at OVP relay, fuel system issues, and the like...he suggested a tired ignition coil or an intermittent charging situation due to worn alternator brushes. He also said to bring it by, he'd scope if for $50 and try to properly diagnose it.

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2002 Ford ZX2
2 x 2013 Honda Civics

If you're at a loss, you might as well get the $50 diagnosis before replacing parts that aren't bad.

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1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma