RJonzie

I read some posts on here I have a 1998 LS400 with 278,000 miles check engine light came on and it said inefficient catalyst bank 2. I changed all 4 O2 sensors about 2 weeks later light came on again inefficient catalyst bank 2 so I bought new converters changed them out the light stayed off about 4 months. Now it keeps coming on but this time it's bank 1. I thought maybe it might be a leaking gasket before the post converter O2 sensors so I replaced them it's still coming on showing bank 1. I replaced the mass air sensor because the exhaust smelled a little rich but no change in that, still showing bank 1. I hope some one knows what to do I am a good mechanic but this has got me pulling my hair out.

cobalt91

Check the ignition coils. It sounds like unburned fuel is getting into the catalyst.

RA40

iTrader: (6)

What MPG is the car getting now?

billydpowe

iTrader: (1)

if you pulled your plugs you could tell which one was bad

RJonzie

About 20.5 to 21 mpg it has gotten better than that I live in a rural area with very light traffic or no traffic at all it has gotten 23.5 before

RJonzie

I will check the coils and change the plugs thanks I will let you know the results