What's going on?

My LS has been quite down on HP lately.  She has a hard time going up hills and doesn't accelerate that great anymore.  I just got an oil change and put full synthetic in her and cleaned my air filter.  Also I put fuel system cleaner in her last oil change.  Seems to be no oil leaks from gaskets or anything....what could be going on???  By the way, she sounds fine....little to no knocking but quite a bit of hesitation.

Have you changed the fuel filter lately?

What year is your car and how many miles. it could just be the spark plugs and old wires.

im not sure about the fuel filter.
 
my car is a 2002 LS and it has about 60,000 miles.

I have also been down on MPG....last trip i made i got about 27 MPG....it is usually about 32....

Do a good tune up....
Spark plugs and fuel filter......
Also get some throttle body cleaning spray and clean the throttle body out (do this before you change the plugs)
I think you said that you cleaned your air filter. I would go ahead and change it as well.

should i worry about new spark plug wires? 

Most of the newer car cars from mid 90's, the wires will last for about 100,000
Inspect them. If cracked or if they have been rubbing on something then yes I would replace them. If no then NO

i saw on a post a while back something about seafoam products....should i do the entire oil, fuel, and air intake system clean???

Here is something else to think about too
 
On the older mid to late 90's and early 2000's
The O2 sensor can start to fail without setting codes. But it can effect engine performance. If I can find the article that about 20 sensors I will post it. It is worth reading..... Talks about early o2 sensors vs newer ones of today.

cool...that would be great. i will look into it.

Yeah, I've heard about O2 sensors going out by not sending the correct voltage to the computer, but the voltage is still within the threshold of the computer thinking it's working.  For instance, your O2 sensor could be off a little bit telling your computer it needs to be more rich when it actually doesn't need to be.  But it's not completely shot.  GM says not to add any additives to it's vehicles.  They say that it can do more harm than good.  I would look at changing your fuel filter first.  They are supposed to be replaced every 30,000 miles.  If it's a little plugged you'll be looking at loosing performance and mileage.  Besides, it's the cheapest thing to replace.  If that doesn't help, I'd look into plugs.  I good set shouldn't cost you more than $40.  I hope this helps!

this may be a shot in the dark but ,my 02 LS with 78,000 miles on it had a serious problem with lack of power. Turns out that the cat. converter was bad. there is a service bulletin about it. The warranty was extended for the cats. to around 100,000 miles. My dealership took care of it at no charge. That may be something worth looking into. 

have your Cat converter checked.
will cause
decressed gas milege
decreesed power
decreesed idel preformance
feeling of slugishness in the car etc...
 
basicall it will start to choke the car off till it wont run any more.
if you ahve done a tune on the car and it still is doign it this is most likely the coulprate.
good time to get the down pipe everyone is talking about and a 02 sim.
good luck let us knwo what ya find.

yes, that sea foam products are really good...we're putting it in stock here now because of demand for it...
 
if your changing the plugs on the car you may as well go out and buy a set of lifetime warranty wires for your car..they're not that expensive..and everytime after when you change the spark plugs you can take them back and say they're missfiring and get another set of wires and buy another set of plugs
its definetely worth it if your changing the plugs to change the wires...i dont care how many miles your @. 

thanx guys....i will let you know how it turns out.
 
appreciate the help....

quote:

ORIGINAL: HaRvArDaLe

My LS has been quite down on HP lately.  She has a hard time going up hills and doesn't accelerate that great anymore.  I just got an oil change and put full synthetic in her and cleaned my air filter.  Also I put fuel system cleaner in her last oil change.  Seems to be no oil leaks from gaskets or anything....what could be going on???  By the way, she sounds fine....little to no knocking but quite a bit of hesitation.

 
 
 
By the way did you  ever figure out this problem? just curious.

Sounds like your catylic converter is bad to me. GM upped the warranty to 140,000mi on these because of the problems. My first went out at 85,000mi (on my '01), and the second went at about 105,000mi (defective).
Same symptoms, poor power. Finally clogged totally, and barely got it to the service garage.
I got re-embursed from GM on the first one, NAPA replaced the second one.
The only ignition problem I had was a bad coil-pack, but I had to replace plugs and wires to figure this out. Plugs just don't wear out anymore. This was at about 80,000mi.

yes the sea foam products work great, i've only heard good stuff about them :)
 
clean out your entire system really well

It was the top end HP, going up hills, passing, etc. that I had problems with, also. Tranny shifting funny is the MAJOR clue to a bad cat.
If it idles ok, like at a stop light, then your fuel injectors are OK. When my idle gets rough, I then use Seafoam, also. Cheap gas has been a big problem for me. I quit buying gas from independent gas stations, and try to buy only Shell V-power or Amaco ultimate for my L-67.
It doesn't sound like an idle problem, but a going up hill problem. I still say the cat' converter is clogged. Check with your local chevy dealer about GM replacing it if that's it. Only a back-pressure test will confirm it.