cyde01

I recently bought a used SC400 in CA but it's not passing smog. I was told by the mechanic that I need to change the O2 sensors and possibly the cats. Couple things:

I was strongly urged to buy OEM sensors from the dealer. I found Denso branded O2 sensors online but I was told that they are not the same as OEM sensors. Is this true?

I was also told that if I have to replace the cats I will need to buy OEM cats from the dealer for it to be legal. The only thing is, I found Magna Flow cats online that say they are California legal. If they are California legal then they're legal, right? I don't understand why I can't use something if it says that it's legal in the state of California.

Can anyone from CA please chime in? Could use some help here.

6SOARER

iTrader: (20)

What did your car FAIL? Emissions? Visual ? Functional?

From my experience aftermarket O2 sensors will function the same as OEM. I seen a lot of repair shops replace bad O2 sensors with aftermarket ones and would do the job.

As for the catalytic converter, if its CA approved and your vehicle is pre 95 you should be OK. If your car is a 96+ OBD2, then highly likely the catalytic converter has to be the right application meaning it has to have the correct OE/CARB#'s stamped on that converter for your vehicle or else it will fail a Visual.

If you need a new converter I would go to your local muffler shop and have them install an aftermarket. You dont want a OEM converter cause that will easily cost you $600-1000, not only that you may need 2.

cyde01

I failed emissions. Hydrocarbons are too high. Everything on the car is stock. So if the car is a 92 and uses a CARB legal cat will it pass visual???

6SOARER

iTrader: (20)

Can you post up the results? How bad did it fail or did it barely failed? Is that the only emission it failed? Have you done anywork to it since you got it or was there any recent repairs you know of?

If it barely failed I say do a tune u(plugs, wires, oil change) but if it failed pretty bad you may need a new converter. Replacing the catalytic converter should be your last option.

If you dont fix the initial problem your new converters will get damage and you will need to replace them soon again.

And YES to your question. The muffler shop should give you an approved converter for your vehicles year, make and model.

cyde01

i'll post the results when i get a chance. were nearly double the limit. according to the maintenance record the plugs and wires were changed recently so they don't know what else it could be besides the o2 sensor or cats. they made it sound like everything else has already been done. they didn't mention the pre 95 cut-off so they made it sound like my only legal choice was to buy oem cats, which i can't afford.

6SOARER

iTrader: (20)

How many miles on the clock? Is the car running GOOD? POOR? Missing?

If it failed HC really bad. I would look to see if your ignition system is in working order. Make sure no plug wires or cut, crimped or arching and that you dont have any broken or disconnected vacuum lines.

HC-HydroCarbons is UNBURN FUEL. Anything that helps burn fuel will help reduce HC's.

Superjatt

iTrader: (1)

Send me pm =]

broda805

iTrader: (6)

I bought an aftermarket O2 for my acura n it didn't work and I cut the wires to my length so I was out 100$ on top of the 297$ dealer one oem one worked fine n the aftermarket would just throw a code. So make sure the O2 yourr getting works for sure before you drop money on it

account2x

iTrader: (5)

Yes, if you buy the right ones. DENSO makes two different types of Oxygen Sensors. A universal part that you have to splice in and a direct swap. The direct swap part is the exact samething as the dealership but half the cost on Amazon.

cyde01

the car has 133k miles but is running pretty good. i ordered some densos but i'm not sure if they are universal or the direct swap. this is the sensor i bought: http://www.amazon.com/gp/product/B00...ef=oss_product

brad11140

iTrader: (3)

I just did a major tuneup on my SC400. The previous owner had a problem getting it to pass smog and it just barely squeezed by after they changed the sub cat on the backend. When I was doing the major tuneup I noticed that my sparkplug tube seals were leaking pretty good meaning it was burning oil. My sparkplug threads were soaked. I am not a smog expert, but would burning oil give off extra HC? (to those who might know) At any rate I changed plugs rotors and wires. I see absolutly no problem with going with aftermarket sensors. Look good because the magnaflow converters are universal, meaning they dont have the flanges and would need to be welded in I believe. There are CARB approved direct fit replacements out there and I think they were somewhere around $110 a piece. Dont forget you have 4 O2 sensors.

brad11140

iTrader: (3)

I am off a bit on the price. Looks like about $165 each for the direct fits.

http://www.catalyticconverterwarehou...SC400&mode=OEG

6SOARER

iTrader: (20)

It may work but remember brad said in his post, you have 4 O2 sensors. You have to test to see which ones are bad. I would google, how to test 92 Lexus SC400 O2 sensors. The later models have 4 wires O2 so its differs from yours.

O2 sensors detect how much oxygen is in the exhaust system. To be honest, I dont know if this is going to fix your HC problems. I see shops replace these sensors when the ECU is throwing a O2 code and, when they do tests to determine that there bad sensors(LAzy O2-sees too much air or too much CO content in the exhaust stream).

cyde01

the link i posted above are supposed to be for the front sensors. i bought 2. i was told by the mechanic we should test the front 2 and if it still doesn't fix the problem then replace the back 2 and the cats. does anyone know parts #s for the direct fit replacement sensors?

darn it looks like the mechanic kept the paperwork with the test results. according to the paper work they gave me the EGR system is functioning normally, coolant temp sensor is operating normally, spark plugs, wires, ignition module, all operating normally. o2 sensors in the front are really slow to respond while the back 2 are stuck at a constant 5 volts.

edit: are the DEC cats really direct fit?

account2x

iTrader: (5)

The amazon link is the correct sensor. Denso uses the term O.E. Manufacture versus O.E. Universal to distinguish the direct swap sensors.

Your mechanic is knowledgeable. There are 4 oxygen sensors but only the two before the catalytic convertor as used to tune the car. The rear two are just in-place to insure the cat is working. It would be a waste of money to replace them unless they give a code.