Check intake gasket by spraying carb cleaner around intake and head mating surface if idle changes then a bad gasket is in play. A lean code on bank one or two possibly both should show when computer detects. Does it seem to run good off idle? Also check plugs for proper gap or burnt electrodes.
Engine miss and no codes
i woul tend to look at mecanical part since ecm not setting any codes
check compression check valve lash may be a valve not opening or closing properly (out of adjustment)
all i can think of now
unless your check engine light bulb is burnt should light up when you first turn key on
SOURCE: Suddenly started missing badly and backfiring at
could be a mass air flow sensor, or a bad fuel pump.
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:-----
Bad miss at idle?
http://technoanswers.blogspot.com/2012/01/bad-miss-at-idle.html
-----------
Stumbling and stalling at
idle after engine rebuild?
http://schematicsdiagram.blogspot.in/2012/03/stumbling-and-stalling-at-idle-after.html
------------
1999 Ford F-150 Idles rough and quits when gas
pedal is pressed less?
http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html
---------
Engine stumbles coming off idle when warm?
http://repairhelpcenter.blogspot.com/2012/01/engine-stumbles-coming-off-idle-when.html
------------------
Erratic idle on car?
http://schematicsdiagram.blogspot.com/2011/12/erratic-idle-on-car.html
-----------
Cold start problem and vehicle shudder around 2500 to
3500 rpms
http://repairhelpcenter.blogspot.com/2012/10/cold-start-problem-and-vehicle-shudder.html
----------
Low idle when cold out side?
http://repairhelpcenter.blogspot.com/2011/12/low-idle-when-cold-out-side.html
-----------
GMC Sonoma Stalls and idles low
http://technoanswers.blogspot.com/2012/10/gmc-sonoma-stalls-and-idles-low.html
--------
GMC Idle Air Control (IAC)
Valve Replacing?
http://schematicsdiagram.blogspot.com/2011/12/gmc-idle-air-control-iac-valve.html
-------------
1996 Camry intermittent
engine failure while idle?
http://repairhelpcenter.blogspot.com/2011/10/1996-camry-intermittent-engine-failure.html
------------
Engine quits at idle?
http://repairhelpcenter.blogspot.com/2011/10/engine-quits-at-idle.html
-----------
Car overheats and Air blows
hot at idle?
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
-------
While stop engine idles
like cylinder missing?
http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html
---------
Idle flair is noticed on car? Rough idle? car
will not idle? Erratic idle speed?
http://technoanswers.blogspot.in/2012/02/idle-flair-is-noticed-on-car-rough-idle.html
--------
High rpm in neutral? Inconsistant high RPM in
neutral?
http://technoanswers.blogspot.in/2012/02/high-rpm-in-neutral-inconsistant-high.html
-------
Vehicle stumbling at idle
and shows code 54?
http://schematicsdiagram.blogspot.in/2012/03/vehicle-stumbling-at-idle-and-shows.html
----------
Rough idle, staling and Erratic shifting?
http://technoanswers.blogspot.in/2012/03/rough-idlestaling-and-erratic-shifting.html
-----------
While stop engine idles
like cylinder missing?
http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html
---------
These
details will help.
Thanks.
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