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Old 11-01-2002, 07:41 AM
Registered User
Join Date: Nov 2001
Location: west orange, NJ
Posts: 47
Can anybody help?

Surprised there have been no comments. Really could use some direction for this weekend.
Thanks in advance.

Stumbling under high rpm load
My '91 420 SEL (199,500 miles) idles and drives smoothly but has recently developed a hesitation or intermitent stumbling when accelerating hard. It is most noticable at higher rpms. My mechanic checked the injectors (replaced 1) and could not find any vacuum leaks. I installed new plugs. The old ones showed even combustion. The fuel pumps, gas filters, distributor cap and rotor were all replaced over the last year. I did a check on the resitance of the spark plug wires and found 2 reading 1250 ohms, 5 reading 1300 ohms, and 1 reading 1400 ohms which is out of spec. I think the wires are the problem. Any other ideas?

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Old 11-01-2002, 07:48 AM
it leaks, its german
Join Date: Mar 2002
Location: raleigh nc
Posts: 1,111
Wheres the duty cycle, base co setting affect the mixture across the full range of rpm and will fuel pressure and coolant temp readings.

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Old 11-03-2002, 10:00 AM
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Join Date: Jul 2000
Posts: 638
high speed/load miss

If the wires are original replace them. The insulation breaks down with time and they will start shorting to ground under high load. Don't forget to replace the ends that attach to the pluge. The insulator does deteriorate.
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Old 11-03-2002, 05:29 PM
Registered User
Join Date: Nov 2001
Location: west orange, NJ
Posts: 47
Rechecked the plug wires using a much better ohmeter and find they are all within spec. However, I checked the resistance of the coil secondary (1&4) and it reads OPEN! Yet I get spark. I'm thinking now that the coil secondary is open but I get spark because the high voltage bridges the gap. Under the demand of high load, the weakened spark is insufficient and thus the miss. Thoughts?
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