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**octaneman** · 05-21-2009, 10:34 AM

Hi gmwrenchhead

There could be carbon build up in the intake manifold throwing the throttle position sensor and IAC motor off alignment. Check the O2 sensor for ash buildup due to contaminated fuel. Also check for open or closed loop the readings on the O2, should be between .45 and .9 anything out of spec means a sluggish O2 sensor. If it is really rough, check for vacuum leaks using propane torch probing around major vacuum hoses on the MAP sensor and brake booster.

Do a quick check on the EGR see if it's stuck open.

05-21-2009, 10:34 AM	#2 (permalink)
octaneman Mentor Home Support, Gearhead Automotive Center Join Date: May 2009 Posts: 544 OS: WINXP	Re: 1999 g van stumble stalling issue Hi gmwrenchhead There could be carbon build up in the intake manifold throwing the throttle position sensor and IAC motor off alignment. Check the O2 sensor for ash buildup due to contaminated fuel. Also check for open or closed loop the readings on the O2, should be between .45 and .9 anything out of spec means a sluggish O2 sensor. If it is really rough, check for vacuum leaks using propane torch probing around major vacuum hoses on the MAP sensor and brake booster. Do a quick check on the EGR see if it's stuck open. Last edited by octaneman; 05-21-2009 at 10:47 AM.