emission trouble(high idle & rough running) gmc truck

zeller · 12-12-2006, 11:02 AM

i have a 1995 gmc pick-up when you start it up it has a high idle and cuts in and out when under a load. it is sending three codes which are as follows 15-coolant temp sensor signal voltage is low 34-mass air flow sensor signal voltage or frequency is low during engine cruise 35- idle air control(iac) system problem-can not set desired rpm

any help would be appreciated
zeller

**Midnight Tech** · 12-13-2006, 06:34 PM

Zeller, if the scan tool you're using to pull those codes has data stream capability, pull the data on that coolant temp sensor and see if it might be bad and lying to the computer. The ECM getting the wrong data from will throw everything into a tizzy.
That IAC motor sounds like it may just be bad and not responding to the computer.

zeller · 12-14-2006, 05:18 AM

Midnight Tech, Believe It Or Not I Have Replaced Every Sensor On Or Around The Throttle Body, The Engine Coolant Sensor I Had Thought That It Could Be Bad From The Factory, But Who Knows. I Will Try This And I Thank You Very Much.
Zeller

**Midnight Tech** · 12-14-2006, 08:29 PM

It's possible...we've had parts come in at work that were bad.

12-12-2006, 11:02 AM	#1 (permalink)
zeller Registered User Join Date: Dec 2006 Posts: 2 OS: win98	emission trouble(high idle & rough running) gmc truck i have a 1995 gmc pick-up when you start it up it has a high idle and cuts in and out when under a load. it is sending three codes which are as follows 15-coolant temp sensor signal voltage is low 34-mass air flow sensor signal voltage or frequency is low during engine cruise 35- idle air control(iac) system problem-can not set desired rpm any help would be appreciated zeller

12-13-2006, 06:34 PM	#2 (permalink)
Midnight Tech Admin/Head GreaseMonkey/Igor's alter ego/Grand Exalted PoohBah Join Date: Dec 2001 Location: SC Posts: 2,920 OS: Windows XP Home/Pro SP3/Windows 98SE/Fedora Core 6/RH 7.2 with Autopoint/TAMS II	Zeller, if the scan tool you're using to pull those codes has data stream capability, pull the data on that coolant temp sensor and see if it might be bad and lying to the computer. The ECM getting the wrong data from will throw everything into a tizzy. That IAC motor sounds like it may just be bad and not responding to the computer. __________________ Please post all questions in the appropriate forum. Questions sent by email or PM will not be answered. Sharing my life...with my Imzadi! Interested in Trek gaming? Check out the Dynaverse! Proud supporter of the Carolinas Aviation Museum. If we have helped you in any way, please donate to keep TSF up and running!

12-14-2006, 08:29 PM	#4 (permalink)
Midnight Tech Admin/Head GreaseMonkey/Igor's alter ego/Grand Exalted PoohBah Join Date: Dec 2001 Location: SC Posts: 2,920 OS: Windows XP Home/Pro SP3/Windows 98SE/Fedora Core 6/RH 7.2 with Autopoint/TAMS II	It's possible...we've had parts come in at work that were bad. __________________ Please post all questions in the appropriate forum. Questions sent by email or PM will not be answered. Sharing my life...with my Imzadi! Interested in Trek gaming? Check out the Dynaverse! Proud supporter of the Carolinas Aviation Museum. If we have helped you in any way, please donate to keep TSF up and running!

12-14-2006, 05:18 AM	#3 (permalink)
zeller Registered User Join Date: Dec 2006 Posts: 2 OS: win98	Midnight Tech, Believe It Or Not I Have Replaced Every Sensor On Or Around The Throttle Body, The Engine Coolant Sensor I Had Thought That It Could Be Bad From The Factory, But Who Knows. I Will Try This And I Thank You Very Much. Zeller