93 3.1 lumina intermittent rough running

Need some of the expert help I've been reading on here. My 93 lumina recently started running rough sometimes. Never when it hasn't been driven in awhile. Usually after a short trip then when restarting...it cranks fine but is idling rough...and can tell there's loss of power...like a miss on cylinders. Then, if it sits for a good while will crank up fine again...and may run fine without problem...until the next trip!

I changed plugs, wires, fuel pump, air filter...still have problem. Also was going to change pcv valve but simply cannot find it! Only a tube running from air intake to front valve cover...no pcv there!??? Can anyone tell me where the pcv valve is located. I bought one when I got the other parts so there must be one somewhere!

Thanks in advance for anyone's advice!

I have a 99 LTZ with the 3.8. And I have the same problems as you do.
It might be the coil packs, or possibly dirty fuel injectors. Have you cleaned the throttle body out with with some carb cleaner??
I have been running seafoam cleaner through the system, and it seems to have improved a bit.. Was thinking of just having an injector cleaning done on it. and see what happens.
I live in Chicago, and the rumor is that the refomulated gas that we run in the summer months is hard on the injectors.

I have a 99 LTZ with the 3.8. And I have the same problems as you do.
It might be the coil packs, or possibly dirty fuel injectors. Have you cleaned the throttle body out with with some carb cleaner??
I have been running seafoam cleaner through the system, and it seems to have improved a bit.. Was thinking of just having an injector cleaning done on it. and see what happens.
I live in Chicago, and the rumor is that the refomulated gas that we run in the summer months is hard on the injectors.

Paulfischer you may be right. I'm thinking first try a single coil pak and try it out for awhile on each of the three locations. I guess the biggest problem to diagnosing this is that it is so intermittent. When you want it to act up it won't! I'm also thinking from the posts I've read that it may be the ignition control module....but I read here that when that begins to make trouble it simply won't run. Mine cranks fine and runs fine....but acts up on occassion....and even then it will crank and run....just rough...like not on all cylinders. Oh well...maybe we'll hear from some of these expert folks on here.

mine is like yours, in that it is not does not happen all the time.
I also do this, when it does happen, once i get home I spray come carb cleaner in to it and let that run through. And than it runs fine for a while.
Give it a shot, and see what happens.

Need some of the expert help I've been reading on here. My 93 lumina recently started running rough sometimes. Never when it hasn't been driven in awhile. Usually after a short trip then when restarting...it cranks fine but is idling rough...and can tell there's loss of power...like a miss on cylinders. Then, if it sits for a good while will crank up fine again...and may run fine without problem...until the next trip!

I changed plugs, wires, fuel pump, air filter...still have problem. Also was going to change pcv valve but simply cannot find it! Only a tube running from air intake to front valve cover...no pcv there!??? Can anyone tell me where the pcv valve is located. I bought one when I got the other parts so there must be one somewhere!

Thanks in advance for anyone's advice!
You did not mention changing the fuel filter, try that, it might be the prob..

You did not mention changing the fuel filter, try that, it might be the prob..


Sorry, I realize I made an error in my statement. I DID replace the fuel filter....not the fuel pump...it's fine. But thanks anyway for trying to help!

I am by no means an expert, but it sounds like it could be one or more of your coil packs are acting up, or it could be the ignition module... those components are subject to heat soak, especially where they are located.
see the link below, you can test your coil packs and module yourself if you have a multimeter:

Ignition Control Module Assembly (http://members.fortunecity.com/slade901/automobile/Ignition_Troubleshooting.htm)

Autozone & Murray's both have ignition module test equipment if you don't trust yourself, it has to be off the car though...

the seafoam is a good idea too, it's identical to GM top engine cleaner.

just disconnect your favorite vacuum hose leading to the intake (some people just use their brake booster hose) and put it down in the bottle of liquid while the car is running. (don't let the vacuum suck the liquid too fast, you don't want to risk problems. you may have to keep your hand on the throttle to keep it running. when the can is empty, let your car stall or just cut it off.

Let your car sit about 2 hours, to give the cleaner time to really work. Start your car, let it run for about 20 mins (there will be PLENTY of white smoke, your car is burning off the cleaner and the carbon).

Then change your oil. :thumbsup:

Oh, and your PCV is in the rear valve cover, not the front on the 3.1, If you've used the trick about tipping your engine forward to get at the rear spark plugs, that would be the best time to get at your PCV.

Might be a good time to change the CPS, just for laughs.