Question about 1991 GMC Sierra

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My 1991 gmc sierra will start but i have to feather the gas if I can get it to idle, the MAP sensor needs to be unplugged. I have changed the MAP 3 times with spares I had around.

I have swapped out everything else I can think of.

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1 Answer

Changing parts is not a solution or fix

Testing a vehicle to find a problem is

Once a problem is found, then the solution is
usually there in front of you

It starts
Is the fuel pressure correct?
Feathering the gas,that would pertain to the TPS Sensor
Was that tested?
MAP-no control over that,do you have vacuum leaks
& were any of the maps tested & correct for your elevation
or vehicle specs

Spark Plugs Good
Rotor & Cap Clean
Vacuum Leaks?

Got an IAC Valve at base of throttle body to clean or replace?

Posted on May 10, 2014

  • Shawn Shepherd
    Shawn Shepherd May 11, 2014

    The truck had not been ran for several years, started up with no issues seemed to be running fine. Cap, wires, plugs,rotor were changed ran ok for a bit then would stall after 30 seconds. checked for leaks, changed throttle body and jets new IAC valve, It gets plenty of fuel. when I finally get it to idle clean. without the map sensor plugged in it will drive but has no get up an go! the secont I attempt to plug in MAP it stalls. I live in a small town no mechanics, so no where to text stuff. Jyst been replacing stuff which i also have to order in.



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