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Old 11-30-2010, 12:45 PM   #1
MotorHead Lon
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Join Date: May 2007
Location: Alabama
Posts: 241
90 350 TBI wont idle down.

I have a junkyard fresh 350 in my 90 Silverado. When I put the "new" engine in I swapped my TBI unit the sensors, harness and everything else to the junkyard engine. When I bought the truck it wouldnt idle down when stopping and putting the truck in neutral or between gear changes. The new engine acts the same, so I'm guessing I have a bad sensor. I have had the Check Engine Light come and found a faulty temp sensor, I replaced that and a month later, while a friend was running diagnostics found the temp sensor had failed again, it was reading too hot. I have replaced the temp sensor again, and the truck still idles too high or wont idle down. Other than the temp sensor we found no other codes.

When I swapped the new engine I left the smog pump off and the truck had the catalytic converters removed. Recently sitting at a fast food drive through the truck idled down but I could smell the truck running rich.

Any help puzzling this out is greatly appreciated.
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88 Chevy C1500, step side, LS swap.

98 Crew Cab Dually, tow rig.

03 Dodge Neon. ECTA Ohio Mile record holder.
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