1999 g van stumble stalling issue

gmwrench_head · 05-21-2009, 09:48 AM

we have in our dealership a 1999 g-van with a stumble stalling runs rough no codes problem we have gone through and replaced pcm due to water intrussion and repaired all the pins that had been corroded we have also checked fuel pressure and have replaced the fuel regulator due to the only time it ran better was when we restricted the return fuel line, we inspected the exhaust for plugged cats they are ok, checked and load test grounds to the pcm.cleaned maf sensor did not help. the vehicle has no codes in it anywhere.

**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, 09:48 AM	#1 (permalink)
gmwrench_head Registered User Join Date: May 2009 Posts: 1 OS: xp	1999 g van stumble stalling issue we have in our dealership a 1999 g-van with a stumble stalling runs rough no codes problem we have gone through and replaced pcm due to water intrussion and repaired all the pins that had been corroded we have also checked fuel pressure and have replaced the fuel regulator due to the only time it ran better was when we restricted the return fuel line, we inspected the exhaust for plugged cats they are ok, checked and load test grounds to the pcm.cleaned maf sensor did not help. the vehicle has no codes in it anywhere.

05-21-2009, 10:34 AM	#2 (permalink)
octaneman Mentor Join Date: May 2009 Posts: 498 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.