Have you cleaned the throttle plate?
The truck ECM computer controls the idle speed based on a number of engine parameters. Idle drops to a minimum preset level when engine coolant reaches normal operating range and the engine goes into closed loop control. This idle is typically set at around 575 rpm, and cannot be changed without reprogramming the ECM. The miss is not caused by the idle speed - unless the engine is tuned properly and has not lost compression, this idle speed can result in a rough running engine at idle (typical with older 4.3L Vortec engines). Best bet is to get a complete tuneup which will include checking the O2 sensors, catalytic converter and cleaning the IAC valve and throttle body.
SOURCE: TPS in a 1998 GMC Jimmy
the tps is ususally at the side of the throttle body opposite where the throttle cable / tv cable mount.
sometimes it won't start, run, or run erratically. there are ways of testing this unit (by output voltage) before you commit to buying a new one. to test it you will need a dvom (digital volt ohm meter).
just a note: straight from the book... "a broken or loose tps can cause intermitten burst of fuel from the injector and an unstable idle because the ecm thinks the throttle is moving."
SOURCE: 2001 gmc jimmy engine warm but heater blows cold air
Disconnect the heater hoses from the water pump and the intake manifold. Get a compressor and blow out the hose (put the air hose into the the hose that came off the mainfold. then flush the system and replace the antifreeze.
SOURCE: how do i bypass security on 98 gmc jimmy 4.3
Hi: Sounds to me like you tried to start the vehicle with something disconnected in the security system. If this is the case the solution is simple. Put key in ignition and turn to the on position, leave on for EXACTLY 30 minutes... then take key out, wait 5 minutes then start vehicle. Hope this helps... please rate suggestion... ty
SOURCE: 1994 GMC Jimmy engine runs rough when cold; smooths out when warm
you need to have the codes checked to know what direction to start repairs,Autozone does this for free
It can be issue
with IAC( idle air control valve) causing the problem.
There
are many other possibilities causing these idle issues. Engine idles rough.
There
are few help links with solutions to troubleshoot such idle issues.
I
suggest you refer the link below and follow
its troubleshooting details:------
Click
the link below:-----
-----------
http://schematicsdiagram.blogspot.in/2012/03/stumbling-and-stalling-at-idle-after.html
------------
http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html
---------
http://repairhelpcenter.blogspot.com/2012/01/engine-stumbles-coming-off-idle-when.html
------------------
http://schematicsdiagram.blogspot.com/2011/12/erratic-idle-on-car.html
-----------
Cold start problem and vehicle shudder around 2500 to
3500 rpms
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http://repairhelpcenter.blogspot.com/2011/12/low-idle-when-cold-out-side.html
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http://technoanswers.blogspot.com/2012/10/gmc-sonoma-stalls-and-idles-low.html
--------
http://schematicsdiagram.blogspot.com/2011/12/gmc-idle-air-control-iac-valve.html
-------------
http://repairhelpcenter.blogspot.com/2011/10/1996-camry-intermittent-engine-failure.html
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http://repairhelpcenter.blogspot.com/2011/10/engine-quits-at-idle.html
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http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
---------
High
Idle Problem
http://repairhelpcenter.blogspot.com/2012/10/high-idle-problem.html
-------
http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html
---------
http://technoanswers.blogspot.in/2012/02/idle-flair-is-noticed-on-car-rough-idle.html
--------
http://technoanswers.blogspot.in/2012/02/high-rpm-in-neutral-inconsistant-high.html
-------
http://schematicsdiagram.blogspot.in/2012/03/vehicle-stumbling-at-idle-and-shows.html
----------
http://technoanswers.blogspot.in/2012/03/rough-idlestaling-and-erratic-shifting.html
-----------
http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html
---------
These
details will help.
Thanks.
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