95 Lesabre Missing Severly

3.8 engine - missing badly in 1st and 2nd - SEVERLY in 3rd (Automatic trans). Have changed plugs and wires and fuel filter. 1st couple times it happened and cleared up (did insert gas heat - don't know if that was why or not) in a couple hours. Next time it didn't clear up - and mechanic friend said he found wet plug in #2. cleaned & put in diff cyl and problem stopped for a couple days. Then I replaced all plugs etc. and it still has not stopped. seems to go from running on 5 cyl to 4 with the way it chugs and lags. MPG cut about in half. Am going to sons house tonight to look at injectors, but really have no idea what we are doing from this point on. HELP please?

This is one of those situations where it is better to bite the bullet and take it in to the dealership and have them diagnose it (but not necessarily fix it!). It could be several things and without proper equipment, you're looking at an expensive game of "replace the part and hope it fixes it." I've played that game and kicked myself for spending tons of money replacing perfectly good parts. In your case for example, you might next buy a crank position sensor, then a coil/distributor set, then new injectors (even aftermarkets were $40 a piece when I did this once), then a new computer for the car, etc. etc.

Although we could make suggestions, this problem isn't one that lends itself to a common fault type of diagnosis. You might have to pay $100-300 at a dealer to fix this, or get you to where you can fix it, so I recommend that route.

I think it is a good idea every so often to get a car to a dealer just for general diagnosis. Have them check for all codes on all systems and what not. They have the expensive equipment and for many things, this is the only way to detect problems.

Nevertheless, if the dealer is not an option, see if the injectors are getting a consistent spark. Test the injectors themselves for resistance. Think about any other external factors which influence when this happens. Is outside temperature or moisture in the air to blame? Is the problem related to when the car is running (cold engine versus warm engine, etc.). Is it more under load or more when idling, or coasting, etc. Have you tried a higher octane gas just to see what happens? (not impossible to get some skunky gas)

Why was the spark plug wet? Are your piston rings so worn that oil is getting up in the combustion chamber? (if so, you are looking at an engine rebuild)

Do a compression test on your engine to check it's general health. Does your car rattle from worn or misaligned valves (indicating a worn cam shaft, or bent push rods) Is your timing chain worn out? Has the car been mechanically abused anytime in it's life (hot rod driving)? Does your transmission make that "old GM" rattle that means the tranny is going? Are all your vacuum lines good? Is your air filter clean? Is your Mass Air Flow setup clear of obstructions? Has this car been run out of gas several times in it's life? (which could cause excessive sediment to get stirred up and cause missing) Have you checked your fuel pressure? (the fuel pump could be going)

Now you see why I think a trip to the dealer can be beneficial in this type of instance--so much can be the cause!

Good luck.

Thank you so much for a very informative answer and suggestions. We found one injector "bad" and replaced it - so the disaster of the moment is solved.
But I will do as you suggested - and get her analysed - that is a very good suggestion. Not financially feasable at the moment - but has gone on my "list" of things to do as I can afford it.

Thanks