1992 oldsmobile 88, idles rough and when starting from a dead stop it misfires pretty bad but once the revs get up its goes away for the most part. what can cause this?

ever tune it up? ever , or at the 60k mile points?
if not why not.
does the CEL lamp glow running>?
rough idle is called misfire.
stalling can be many things, a mech sees this all in 5min.
here on the form i have to ask many questions (cant drive it)
lets play that out.
1: i start car and ask owner, ever tune it up,: blank stare.
2: i see it dont reach 180F coolant temp,. (bad thermostat)_
3: then note misfire. i tune it up and its fixed. or
4: it still misfires,, i find the EGR stuck open. (listed under service 60k)
5: it still misfires, i find idle too low, the ISC is stuck closed.
i clean the EGR and ISC valve and car now idles ok,
but is still rich , i find the 02 front sensor long gone bad.
it looks like it has cancer.
there are over 50 causes for misfire,
1 or all 6 cylinders. what we do is start with basics and work up.

here are 2 hints on stall.
first off the ECU failed to stop the stall, its programmed to do that
using the ISC .
so it failed to work.
the EGR stuck open will do that every time or idle at 500RPM
and shake the engine hard, misfiring.
or if one cylinder or more is dead.
or if the ISC sticks closed.

so when it seems to stall, pre-stall, as RPM drops below 800 rpm
you use a fast right foot. is it easy to prevent the stall?
easy,save, is isc stuck closed? gummed up.
harder is EGR stuck open, (but you can correct it by hard actions of right foot)?
impossible to stop the stall.?

your mech, does all that action in 5min. flat.
even loss of 12vdc power to EFI systems , do this.
(cant save it) and mech sees dash lights go dead. bingo no DC power, all by looking and seeing. and feeling.

he gathers evidence,


both my 4.0L jeeps, loved to stick the ISC.
every 20kmiles, off it cam and got sprayed with
Klondike gun lube, Dry lube. no oil , it looks like brown paint
and acts like Teflon.
The 4 liter likes to get he PCV oil mist up to the ISC,
this builds a film of gunk on the valve cone inside .
im not saying this is it, but the easy save above is a big clue.

Do a compression test.

i would check the injectors for leaks first

For engine misfiring problem check the help links mentioned below. Click the link below to go through the troubleshooting procedure :---- Engine misses and truck jumps? Hard to down shift? Issue with high gear only? http://technoanswers.blogspot.in/2012/02/engine-miss-and-truck-jumps-hard-to.html

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Bad miss at idle?

http://technoanswers.blogspot.com/2012/01/bad-miss-at-idle.html

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While stop engine idles like cylinder missing?

http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html

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Engine Misfire codes for car?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html
Engine Misfire codes?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html

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Misfire on cylinder 4?

http://schematicsdiagram.blogspot.com/2011/12/misfire-on-cylinder-4.html

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Oil on spark plugs and car misfires?

http://technoanswers.blogspot.in/2012/02/oil-on-spark-plugs-and-car-misfires.html

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This will help.

Thanks.

Hello, I have 1996 Ciera with rebuilt engine pretty new, also fuel filter and fuel pump replaced but I have a problem, the car starts and runs well cold but once car has been running for a few hours, either stopping or coming to a stop it starts to idle roughly and has come to a stop at different occasions. Check engine light does come on and off occasionally. Can you help?

HEAD GASKET GONE

car starts and idles good.it cuts off while driving,and starts right back up????????

Take all of the belts off for a short run at idle. If the sound goes away it is pulley related, spin each pulley and listen for bearing noise, also check for play at this time.

If the noise does not go away when the motor is driving no accessories you have a more serious problem.

the idle air contoller,or thecoolant temperature sensor,which when cold sends info to the ecu to idle fast

well spend some change and have a simple tune-up.  Plugs and filters and readjust the idle.