Changed both bank 1 o2 sensors. Changed Spark plugs, cleaned MAF sensor and throttle body.

Took it to two exhaust shops. Both said no exhaust leak, second shop said front right catalytic converter is bad. Quoted me $600 to change it. I’m weary though because everyone says the gs 300 catalytic converters don’t go bad.

Any ideas/advice?

 

After digging around I think the P0171 might be the cause of the p0420 code. I’m going to look for vacuum leaks tomorrow. Hopefully if that clears up it stops giving the p0420 code as well. It doesn’t make sense for the cat to go bad if everyone here says the cats on this car last a long time.

Also found very small amount of oil in the coolant... will have to figure that out as well...

 

Did a vacuum test with a mityvac and it was holding at 20 Hg. I tried a smoke test with a cigar but didn’t see anything because I had such little smoke from the cigar. I tied a bicycle tire pump and was pushing air through one of the intake openings and I hear a faint hissing sound in the back of the intake manifold but I can’t spot the leak. When I turn on the car and get close at times I can hear the hissing noise as well.

 

Just added some BG 44K to clean my fuel system. Looking for someone to do walnut blasting for a reasonable rate in Los Angeles/Orange County/Riverside. Going to call around some more places tomorrow. Also going to try the seafoam cleaning of the engine.

If anyone has any advice please post away!