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Old 05-23-2016, 01:27 PM   #12
CHEVYJEFF
 
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Join Date: Sep 2014
Location: WYLIE TEXAS
Posts: 28
Vehicle: 1997 D21 HARDBODY
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went thru this with my 97 recently.

due to an antifreeze leak creating air pockets around temp sensor and bad upstream o2 sensor (checked ok via tests but was bad). the engine would go into open loop at idle and emission sensors would never reset. never threw a code either.
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