94' Lesabre rough idle, loss of acceleration...

After what seemed to have been two rough fills of gas recently my Lesabre which is in great shape, timely maetenence and runs great has started to run rough and doesnt have as much power driving down the road.

After the first bad tank it ran fine after a few weeks and a few refills later then the supposed 2nd bad tank of gas occured.

I recently installed new plugs which helped some and then filled up with highest octane gas which helped more so, however it still sometimes doesnt have enough power accelerating and tends to run rough/shake abit around 50-60mph.

I plan on installing a new fuel filter this weekend after ive got the gas tank very low, and shortly will install new plug wires.

Any other ideas?

Im not a mechanic, but you said u replaced the plugs and not the wires, try repcing the wires

I'm no expert, but I recently had to replace the crankshaft position sensor (CPS) on my 94 ... during the diagnosis I learned that the Camshaft Sensor (that's not the same as the CPS despite the similar names) can cause the symptoms you describe ... running rough, loss of power, bad mileage. No idea if that's your problem or not but it could be something else to explore. See the lengthy thread "95 Lesabre Dies without warning" for my situation and resolution.

Where is the crank shaft position sensor and about how much was the cost?

The Crankshaft Position Sensor is located under the vibration damper, which is under the timing chain cover. The part itself is cheap ($30) but getting to it is a bear ... I decided to let Firestone do it for $151 including the part, because the Haynes manual said that it involves taking off the right front wheel, wheel shroud, serpentine belt, timing chain cover, and vibration damper, all of which is considered a 1.1 hour job (yeah right). One of the other guys on the other thread did it himself and I think regrets it ... I got my car back this morning and have put about 40 miles on it today without one stumble or stall-out ... my CPS was cracked in half, Firestone said, so in my case this was the accurate diagnosis. But if your car is not "stalling", just running rough, that doesn't mean it's the right diagnosis for you. My car ran great 90% of the time, then quit, then started right up again and ran great again. It did not have a rough idle, nor a loss of acceleration with the CPS, that sounds more like the Camshaft sensor, from what I've read.

No stalls at all, just idles and runs rough.... particularly between 50-60 where it shakes abit.

Where my gas is at seems to play a role, put in some Fuel System Cleaner and it ran fine for about a week then when my tank got low it started up again.

Do you know where this other sensor is located?

I'd be more inclined to suggest you use some gas line drier. Adding a bottle of this (isopropyl alcohol) will help remove any water in the tank. Make sure you buy isopropyl and not methanol. Iso is for fuel injection and carburated, methanol is only for carburated. The Iso costs a little more, but you can't go wrong. You aren't getting a check engine light, right? If you are, have it scanned. It'll save time and money in the long run.

Gas line drier eh... never heard of it....

And no im not getting any engine lights...

thats a good point knuckle, i never thought of that. Also, Valvoline does an entire fuel system clean for like, 80 bucks. not just dry gas, but they clean your filters and injectors, i think using high pressure. I got it done at a discount on my car, and it improved my milage and performance. BTW, any gas station will have fuel line dryerm just go to the area that has oil and all that. But like knuckle said, make sure to get iso

How would I have gotten water in my gas tank though?

Water in your gas tank comes from many sources, not the least is when fueling up at a gas station that has it in their tanks and also condensation from heating and cooling.

Have you tried changing the ignition wires (as suggested earlier) yet?

Have not changed the wires, just picked up some dryer today, was cheap... only 99 cents per bottle. will let you guys know how it goes...

Also wanted to mention that this seems likely as I live in Florida and it has been raining ALLOT!!

I added the dryer last weekend and after the second day or so of long driving (I drive round trip of 40 miles or so to work every day) it cleared up.

Has made a WORLD of difference... the car is running the best it may have ever run since owning it.

Hopefully I wont get anymore bad gas. :)

Glad to hear it! Another great liquid preventative is Techron. Use this for a fuel system cleaning every now and then. I wouldn't go crazy adding chemicals to the tank every fill up, but, here and then a little bit helps!

I tried using that before and it seemed to work "ok" for about a week then things went back to running like crap again...

Perhaps I got more gas with water in it or maybe just because it isnt for removing water.. dunno.. just glad all is well now.

Thanks allot for everyones help!

Call me crazy, but I don't think rain can cause water in a tank unless you are driving around with no gas cap ... it probably came from either running around with a nearly empty tank (allowing condensation to build up in the tank) or getting getting gas from a station with a leaking ground tank.

My dad always said buy gas from the newest station around (new tanks = less contamination) and my uncle taught me to always keep the needle above half ... both pieces of good advice in my view.