running rough

[troonbop]

92 lumina has about 150000 miles on it, and was running very well. Sudenly started running very rough and idles rough, but doesn't stall.
A funny thing - the "check engine light" hasn't come on. I'm hoping just plugs and wires, but who knows.
I guess the "rough running" questions get asked a lot, sorry for another one,but this is different, I guess, cause it doesn't stall, engine light doesn't come on, and it starts well.
Any ideas, thanks.

[jsgold]

Hard to always find the culprit but, after you check for wires and plugs problems try removing the idle air control valve and clean it and the area it sits in. Be sure to unhook battery first. It gets clogged with carbon and will cause rough idle. Clean with injector .carb cleaner and do not push on the spring. Other possible items usually are O2 sensor, MAP sensor, cracked/broken vaccuum lines, plugs. The sensors usually show a trouble code though, which you have not got so far. One other possibility is one of your coil packs may be bad, which would need to be fixed ASAP. You either have 2 or 3 (depending on motor, 4 cyl= 2, 6cyl=3. ). Each one controls two plugs and one of them can fail to fire one plug. If you rule out plugs, IAC, etc., try checking for fire on all cylinders. If you find one that is weak or not firing then you need to replace it. They sit on top of your ignition module ( a flat module with wires running to it), and of course your plug wires run into the coil packs. Pretty sure you need to remove as a unit and assemble and install that way if you need to remove them. Hopefully it is just a burnt plug wire ( our Corsica just had one burn on exhaust). Maybe others here will have additonal advice.

[meuhus]

Originally Posted by troonbop

92 lumina has about 150000 miles on it, and was running very well. Sudenly started running very rough and idles rough, but doesn't stall.
A funny thing - the "check engine light" hasn't come on. I'm hoping just plugs and wires, but who knows.
I guess the "rough running" questions get asked a lot, sorry for another one,but this is different, I guess, cause it doesn't stall, engine light doesn't come on, and it starts well.
Any ideas, thanks.

check injectors,fuel pressure, coils, ignition modual
if the check engine light isn't on its usually not a problem with the computer controled circuits
and you will not get a code for low fuel pressure or an injector going bad
or fuel pump or a coil

[troonbop]

Thanks for the help. I changed the front three plugs this morning and it was a big improvement. I think if I could get at the back three my problem would be solved. But that seems to be a whole other story. Who designed this thing?

[meuhus]

Originally Posted by troonbop

Thanks for the help. I changed the front three plugs this morning and it was a big improvement. I think if I could get at the back three my problem would be solved. But that seems to be a whole other story. Who designed this thing?

to get at the back three is not to hard
i thought it was too but not to bad
kind of a pain but it could be worse
any way
first put a jack under the tranny pan (put a board on the jack pad)
rase it a little
then you take out the bolts that are closer to the motor on your
torque strut mount things(dog bones)
then jack up the jack to rotate the motor up
untill you can put the bolt thru the hole on the bottom of the dog bone
to hold the motor from rocking back
or just leave the jack under it
this will rotate the motor up so you can get at rear plugs
this also has to be done to change the knock sensor and crank sensor
and u could also remove alternator to gain more clearance