My 2 week old (used) '07 G is at the dealership right now having the Cat Converter replaced, along with a new A/C compressor (it had the whine).

I'm currently driving around on a '08 loaner. One thing i immediately noticed is the much better fuel consumption on the loaner. Driving the same way, and going the same route, i'm averaging 3-4mpg better. (Traditional way of calculating).

Also, the '08 seems to have a bit more oomph down low, i can more easily accelerate from a stop, casually, without breaking 2.5k rpm.

Could the poor mileage/performance on my own car be caused by the faulty Cat, or did they tweak something on the '08s that make them better?

Lastly, why would a Cat fail at just 14k miles? Should i have the dealership check the engine for leaks, plugs for issues or sensors for premature wear?

Thank you, everyone, for any input.

- Mike

 

IMO poor mileage and performance of the car are directly affected if the cat is no good. not sure what causes a cat to go bad at only 14K.

 

the '08 loaner probably seems like it has more power because the ecu adapts to the way people drive. i drive the loaners a little harder than my own car......well, because it's not mine...the '08s also have a different throttle sensitivity...some ppl like it, some don't...i don't because i like the ability to snap necks

 

I can't answer your question about the Cats but you should check out this TSB.
http://x.infinitihelp.com/forum/show...95.html?t=3495

I'm gonna wait for my car to get out of the dealership so I can double check if I have this issue myself.

 

Thanks guys. I sure hope the new cat fixes the mileage problem - i could barely do mid-19mpg on mine whilst averaging 24 on the loaner.

Interesting note about the ECU learning. I would think that would only apply to transmission/gear changes and not the actual engine output at any particular RPM.

The throttle sensitivity thing is fine with me, the '08 does feel noticeably more linear, however it also emparts a "sluggish" feel off the line. The dealer will be keeping the car for a couple more days, i'll give the throttle TSB some more thought.

Thanks again!

 

My guess is that with the new converter you'll pickup 3 to 5 MPG. They only
replace the converters when they're plugged up, that's very bad for gas mileage. I've seen converters so plugged the car would not run, simular to
covering the exhaust tip....engine dies!

 

Or the cat explodes and catches the grass on fire...


don't ask me how I know...

 

I had my 07 in the shop because some hack scratched my shift **** and it was in being replaced.
My 08 loaner, also an X, was also 3-4 mpg better, but had no power compared to mine.
I could immediately tell that the touchy accelerator TSB was applied and quite honestly, I hated it. My car has that "Snap Your Neck" edge to it and I've learned to control it. It's there when I want it and not when I don't.

I was completely bored with my loaner and couldn't wait to get my baby back.... 18 mpg and all.