1995 GMC Yukon Idle Surge When Warm

[Mule]

1995 GMC Yukon (non-Vortec), ongoing for about a year, after truck was taken out of storage for 13 months:

 

Always smells a little rich.

 

Cold start – Long cranking, smooth idle. Smells very rich.

 

Warm start - no codes, no SES light, warm start (30 minutes off after full hot), short cranking, initial smooth idle; surging idle starts after 20 seconds. Feels like stalling, then catches itself and goes up to 800 RPM, then drops and repeats. Smooth idle and ride after about 1 minute. Smells rich/flooded. Not as bad in the summer, but very bad in cool weather.

 

Overall, it seems like something heats up, cools off, but not all the way cold, then either malfunctions or gives a bad reading to the computer which creates the surging. After a minute, it either warms up enough to stop malfunctioning or giving the computer bad info.

 

I have been to nine shops and they can all duplicate the symptoms, but can not track the source.

 

Thank you for any help!

 

No change after any of these fixes:

 

03 Jan 2012

Replace Coolant Temp Sensor

Replace coolant temp sensor connector

 

11 Jan 2012

PCV replace

 

12 Jan 2012

Replace Fuel pressure regulator

Replace driver’s side (left) fuel injector; it was dripping

 

14 Jan 2012

Clean air filter

 

24 Jan 2012

Replace Dist cap and rotor

Replace ignition coil

Replace Ignition Control Module

Tighten Idler Air Control Motor

 

31 Jan 2012

Replace IAC and pigtail

Replace O2 sensor

 

08 Feb 2012

Replace fuel pump

Replace fuel pump sending unit module

 

05 March 12

Replace fuel filter

 

08 March 12

Replace Spark Plugs (AC Delco Rapid Fire #1)

Replace Spark plug wires and heat shields

 

10 April 2012

Removed Jet chip to aid diagnostics

Replace Throttle Position Sensor

Replace PCV hose

Replace elbow on rear of TBI crankcase breather hose

 

25 April 2012

Replace MAP Sensor AC Delco

 

01 June 2012

Replace vacuum hose from A/C accumulator to heater control valve.

 

02 July 2012

Replaced TBI plastic ring and rear breather vent hose

Sea Foam spray into TBI

 

30 Nov 2012

Re-install Jet chip

Replace EGR valve

[2010LTZ4x4]

That's the heck of a replacement parts list.

I didn't see catalytic converter on there, it could be plugged and you say it smells rich. If its not burning any of the unburnt fuel that could be where your rich smell is coming from. Just a thought.

[Mule]

Suprisingly, the cat converter started to rattle about a week ago. So, solves the problem or not, a new one is on the way. Thank you.

[2010LTZ4x4]

Keep us posted, would be nice to know if the cat was the issue.

[Mule]

I think whenever I do solve this, I will be so excited that I will tell the world! I have seen similar issues on other websites, but there is never a closing solution.