2004 sunfire idle problem

  • Thread starter Thread starter GJM
  • Start date Start date
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GJM

Idles rough, and makes the car jerk when stopped at a light. Once rpm's up drives normal. I've replaced plugs, air and fuel filter and swapped out IAC valve and TPS with another vehical with no change. Fuel pressure is good - 57 psi running and 53 static. Tried taking a vacuum reading at intake duct where the FPR connects but got nothing. What is the vacuum supposed to be at idle and where is the best place to tap into it?
 
Tapped into the intake (removed line from purge solenoid) and vacuum fluctuates from about 14 to 15.5" (needle fluctuates constantly as rpm goes up and down). Opening the throttle increases vacuum and it will become more stable. Anyone know what it should be reading - at idle? - open throttle?
 
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