Truck wanting to die while slowing to a stop

2007 GMC CANYON
112,000 MILES • 3.7L • 5 CYL • RWD • AUTOMATIC
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JUSTIN HANSON
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Truck drives perfectly while I am driving down the road when I go to come to a stop and have my foot on the brake my lights will dim and then brighten back up then dim again. my rpm's as soon as it gets too 2000 rpm's they drop and then the raise and then drop and then they raise and they will drop and then raise. but, if I keep it above 2000 rpm's everything is fine and every now and then it will actually die while coming to a stop. I put a code reader on it in the only code that came back said thermostat temperature too low for operating temperature. my check engine light has never come on. I am lost on this one.
Dec 1, 2016 at 10:48 AM
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WRENCHTECH
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First eliminate all vacuum or air leaks in the system (very important)

You need to try cleaning the throttle body. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, you may need to replace the electronic throttle body.
Dec 1, 2016 at 12:20 PM