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Old 02-20-2001, 04:41 AM   #2
wac
Scooby Specialist
 
Member#: 689
Join Date: Dec 1999
Chapter/Region: NESIC
Location: Lebanon, NH, USA
Vehicle:
2005 Outback 2.5 XT
Champagne Gold Opal

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Quote:
...when the engine shuts off with ignition key on, the reading is 100% accurate.
There's no such thing as 100% accurate. Repeatable maybe, but not accurate.

Back to the original question - it's normal to see noise on electrical lines. The noise is caused by spark plugs, distributors (both electronic and otherwise), electrical fans, pumps, radios, etc. Only worry if the TPS % readings drift by more than, say, 2% with the engine on. It's no wonder the TPS is stable with the engine off...

-WaC
Wayne
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