1991 GMC S-15 Jimmy Logo
Anonymous Posted on Dec 14, 2008

91 jimmy 4.3 will not idle cold or hot

I have replaced or tested the following: fuel pump,fuel filter,ignition module,pick-up coil,plugs,wires,cap,rotor,iac,tps,coolant temp sensor,and it has gotten better. It will starts after cranking a bit and will run if I keep slight throttle pressure and seems to have all of its power, but as soon as the throttle is released for an idle it will stall and sometimes is very hard to start again. I have been a mechanic for over 15 years and this has me stumped. Is there something I am overlooking or missing or could it possibly be the ECM. Ihave retrieved codes from the ECM (tps and O2) cleared and repaired so i figure that the ECM is operating properly.

  • 7 more comments 
  • Anonymous Dec 16, 2008

    fuel pump is running,no fuel spray from throttle body injectors

  • Anonymous Dec 16, 2008

    yes there is pulse to the injectors, i noticed that the fuel pump is running erractic(high then low) it is new but maybe i have a bad one

  • Anonymous Dec 17, 2008

    i was ruling out the fuel pump because it is new, must be bad, fuel pressure is hit and miss ( sometimes there sometimes not) thats why i had no fuel spray Pulling tank maybe kinked vent line

    thanks

  • Anonymous Dec 28, 2008

    I can drive this Jimmy down the road normal,it runs normal and has plenty of power, the only time it stalls or stumbles is when i let it idle. After it stalls in is next to impossible to get running again, when it does start it will run and drive like there is nothing wrong until i stop and let it come to an idle,then it stalls again. As long as I keep the rpm,s up it will stay running. Drilled out the idling screw and bumped the idling, still stalls at idle,could it possibly be the computer or the prom, there is notrhing left. thanks

  • miken277 Feb 01, 2009

    1989 Honda accord.  Idles low and rough, stalls out when applying gas.  When the coolant was low, it would cycle between high and low rpms wierdly, but that fixed it just idles low now.  Will not restart.  Exhaust smells like fuel.  

  • Anonymous Mar 12, 2009

    I have no pulse to the injectors, what make the injectors pulse

  • how can you have pulse and no injector spray if you have the right fuel pressure did you jump the injectors to see if they are opening sound like you have no fuel pressure

  • do you have pulse to the injectors

  • is the egr stuck open just alittle did you take it off and check? or is the pcv broke like an open vac

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rockys performance motors

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  • Posted on Mar 14, 2009
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The distributor module and pick up coil

  • Call me it would be easier @ Rocky's Performance Motors, ask for Joe. (772) 334-0789

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  • Posted on Dec 28, 2008
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I HAVE THE SAME JIMMY, HAD THE SAME PROBLEM, I REPLACED THE IGNITION SWITCH , THAT FIXED IT.

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