10MPG?! 140K 00LS8 with a cat code...thoughts?

[Turboguy]

2000 LS8, mid 1999 build, 140,000 miles, I'm third owner. I just got this thing really tuned up with synthetic Mobil 1 oil & filter, new Walbro fuel pump with new socks, SP-467 Platinum plugs, Visteon 60-1008 coils, valve cover gaskets, 4 Bosch O2 sensors, new inline fuel filter, and a K&N replacement filter. 4 new rotors and pad sets. All parts are OEM replacement, or recommended upgrades.

It idles well, has tons of power, has stock 16-inch rims and decent tires properly inflated, and not too much weight in trunk.

But it does keep showing the P0430 cat converter low efficiency Bank 2 code. It was there before the maintenance work and I hoped that fresh parts and some good long drives would heat things up and maybe fix it, but it comes back after I clear it, along with the "not ready for emissions" code.

My theory is that poor previous-owner maintenance has ruined at least one cat, even though car wasn't hesitating or anything on old coils. But I'm only getting like 170-180 miles to a tank, pushing it to a really low fuel gauge. I live in NYC and only drive around the city now, flat roads, with a mix of 35-65 mph, and rarely sitting in traffic, if you can believe that.

Question1: What the hell?
Question 2: Any ideas on where I could try to troubleshoot? Swap all cats for good high-flows, ?

 

[RigsLS]

Imagine you starting a new thread and then answering your own question.
Not like the car is trying to tell you something with that code huh ?

- - - -

now for the funny answers,

1) did you make sure you put the gas cap back on fully ?

2) have you checked to see if your neighbors are making away with full jerry cans at night ?

3) just drill a 1" hole in the cat that's acting up. it just needs to breath better !





Disclaimer: I'm on the Captain tonight !

 

[M4rk]

Bosch O2 sensors.. hmm. These cars don't seem to like anything Bosch.

 

[jmtiseo]

It's a good possibility that the previous owner drove around with a misfire long enough to damage the cats. The o2 sensors won't instantly fail. I think they're telling you something. Get 'em checked out. Hi-flow cats is a marketing scheme by the way. Just replace with a quality catalytic converter.

Better hangin' out with the captain than THE KRAKEN! The biggest ******* in the sea! Don't want to be around when they release that on here.

 

[Telco]

Bosch O2 sensors.. hmm. These cars don't seem to like anything Bosch.

Neither does anything else. Engine sensors really need to be factory parts or factory supplier parts. For General Motors I use Delphi sensors when I don't use them from the dealer directly. I'm using Delphis on my LS, or you can use Motorcrafts. Rock Auto sells them. Any time I've used or heard about Bosch O2 sensors being used, the user complained about poor mileage. That won't have anything to do with your failed cat though, the Bosch sensors are at least good enough to detect a failed cat. So far as the high flow cats, I'm using a Magnaflow high performance cat on my 2000 Silverado, works pretty well. I don't think they're legal in Commiefornia though.

 

[Turboguy]

BigRig,

As an immigrant to this country (my picture is attached), I don't appreciate your gas can photo. I mop very hard each day to enjoy my LS.
But as you are from Canada, I'll let this one slip...

Seriously though, that code is really recent and I didn't know how far along a cat fail/plug had to be before flipping a code and drastically affecting air/fuel and mileage.

I wondered if this code is similar to how when an O2 sensor goes bad, it instantly throws the A/F rich as a failsafe, hurting mileage. Or maybe my junk has been going bad for awhile...

M4rk/Telco, my bad, originally were going to be Bosch but ended up with Motorcrafts (just checked invoice). jmtiseo, thanks for the input!

 

[RigsLS]

@ Turboguy:

ROFL ... funny stuff right there.
You look a lot like Eddie !

PS: I'm actually European and only came to Canada to buy/drive an LS.

 

[M4rk]

 

[RigsLS]

Hahahaha you're killing me here M4rk !
Whatever makes you happy ...

Having a little fun makes me a troll ?
Please !!!