IvanHD

Hi guys,

One more post on P0430 and bad catalytic converters.

All started six months ago when I decided to have my spark plugs replaced (GS 3rd, 450h, 2006, ~240k km). On the very next day the engine light came on. Cool, I thought, that must be something with the new spark plugs which they will fix easily. Totally wrong - six months later and expensive testing led to nothing. According to the technicians, they can't blame spark plugs for P0430 and certainly that 18 year old car just need a new cat. Since then we are trying to resolve the issue in all possible - replaced O2 sensors, added extensions, even bought a new catalytic converter (aftermarket one, $1500) - none of that worked! It's shoking that just after a 10 minute drive the check engine will lit up again.

As you can sense my question boils down to - does anyone believe there might be indirect connection between "potentially" bad spark plugs and P0430?

(by the way, the original catalytic converter looked better than the new one, which was kind of disapointment)

Oro

MIT engineered fix.

You can buy pre-made emulators, or make your own for about $10.

93SCMax

Did you replace the A/F sensor and the O2 sensor with OEM parts? If you didn't then you made a big mistake and wasted a lot of $ on a catalytic converter. P0430 and P0420 codes are common. Replacing catalytic converters is not.

Bad spark plugs can cause a "carbon" issue. Using good fuel and injector cleaner will help.

ibidu1

iTrader: (1)

First off what car is this? GS350 460 rwd or awd?

Second, what spark plugs did you use and where they purchased from a reputable source?

Third majority of cat failures happen because of exhaust leaks. Did you take the car to an exhaust shop and test for leaks. Especially at the mid pipe.

IvanHD

First off thanks for helping! From the original post - the car is 450H - it's only rear wheel drive and the idea with the bad exhausts leaks was first thing to check. It turned out 450H does not have the same exhaust construction and unfortunately for me does not suffer from same issues as other lexuses.

As you asked about the spark plugs - the funny thing is my old spark plugs were aftermaket and new ones are OEM.

IvanHD

Oro, that's really interesting! None of the technicians has talked about this trick so I am going for it! (surely not going for OEM cat) Will let you know the result.

Thanks a lot!

ibidu1

iTrader: (1)

Ya 450H is a different exhaust, when you say you checked the exhaust did you examine it throughly? Maybe have someone block off the rear tail pipes with a wet rag. While you or someone else under the car listen for hissing sounds?

Your OEM did you purchase them from the dealer or from ebay or amazon? Theres so many fake spark plugs on the market, a fake plug usually doesnt have the resistance in it to match the oem plugs or denso plugs. So it creates havoc, like misfires. Usually what kills cats are misfires.

You can also test the cat to make sure it is flowing properly by using a lazer temp gauge. Measure front and rear of the cats, and compare it with the other side. If the exit is much cooler then it could possibly be the cat is burnt internally. I would try to look for a used cat if its possible.