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Hesitation and sputtering


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  #1  
Old  May 4th, 2012, 10:45 AM
  • CF Beginner
    Join Date: Aug 2010
    Posts: 4
Hesitation and sputtering

I have a 90 Chevy 1500 with a fuel injected 350 that hesitates when accelerating from a stop. Replaced fuel pump, coolant sensor, oxygen sensor, throttle positioning sensor, I even had an extra set of injectors I tried and nothing works. Runs ok after it gets going but is about to drive me crazy. Any suggestions and could it be the computer-no codes??

  #2  
Old  May 4th, 2012, 10:59 AM
Fuel filter? Possible IAC motor.

Allan

  #3  
Old  May 4th, 2012, 11:01 AM
  • CF Beginner
    Join Date: Aug 2010
    Posts: 4
Done the filter. What is IAC.

  #4  
Old  May 5th, 2012, 6:57 AM
Idle Air Control step motor; screws into the right side of the throttle body. Big fat thing, takes an 1" wrench to loosen if I remembr right.

A 'bog' or hesitation is caused by the mixture being way too lean.

The IAC's function is to set the mixture when the engine is cold and before it goes into closed loop. However, if this thing is 'mechanically' stuck in the open position, it would act must like a vacuum leak in closed loop.

Not saying this is your issue, just trying to help you eleminate another possibility. Does the engine idle too fast? Higher than about 600 rpm ?

Allan

  #5  
Old  May 5th, 2012, 9:41 AM
  • CF Beginner
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    Posts: 4
I will give it a try. Thanks for your help.

  #6  
Old  May 7th, 2012, 9:48 AM
  • CF Beginner
    Join Date: Aug 2010
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Allan- You are the man! Had an extra injector housing and swapped controls and runs great again. Can't thank you enough, talked to many people and that was the first time I was told about the IAC. Thanks again.

  #7  
Old  May 7th, 2012, 5:10 PM
  • CF Active Member
    Join Date: Aug 2011
    Posts: 109
    Houston, Texas
could this be the same problem on a 97 k1500 350? i have only i bought the truck about 5k miles ago, and the only fuel part i have changed is the filter.
i only have the hesitation on my first takeoff after the truck starts


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