Question about 1991 Chevrolet C1500
There are numerous things that could cause this. Something I do on mine every 6000 miles is get a can of carb & coke cleaner. I start the truck, and rev to 3000 rpms then I spary cleaner directly in to the TBI. This cleans pretty much everything out that has been built up over time. (Truck will try to die when performing cleaning. Keep sparying and up the amount of throttle just enough to keep running.) Now since the truck is a few years old I would next CK the vacum lines. They run all over the top of the engine as most people know but also on your truck they are what run the air vents moving from floor to vent to defrost, and if 4x4 the front axel hub locks. There is a vacum line that runs from TBI to the vacum canister (located on driver side behind head light) Then it runs down beside the radiator to the frame rail then down the frame rail to the cab. This line is mostly metal (just like the metal brake lines) and it seems get holes in it from it rubbing all sorts of ****. Then I would ck the throttle postioning senser, and timing. Also on these trucks the idle will be around 200 to 400 rpms higher in Park or Netural then if in Reverse or Drive. If it does not change more then likely you are having either problems with a sensor in the transmission, or Computer problems. Also if you have a TBI spacer it will rasie your idle most the time. If you dont have a spacer you will also want to try this. (you never know if someone else may of adjusted it) You will need to adjust your idle screw. NOTE: Keep track of exactly how much in or out you adjust this screw. This way it can always be returned to stock.)
Posted on Aug 08, 2008
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Posted on Jan 02, 2017
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