Please help..... new to the forum. I took my 92 sc300 for inspection last weekend
in a private garage but fail NOx emission. The HC and CO are pass. I brought the
car last NOV. and put in the garage and warm up the every weeks or so for the winter.
The car pass everything beyond standard with previous owner. The garage couldn't fix or
adjust the emission. They asked me to bring to the Lexus dealer. anybody has this problem
before... and how about to fix it. What the wrost case that need to be fix. Should I just bring
it to the Lexus dealer.....any help will be presiated.

 

drive around, maybe cruise on the freeway for a good amount of time like an hour, drive with OD off or dont use 5th gear, get the car nice and warm and when you do that you can try again, you might want to just get the car sniffed and not run it through the computers yet

it sounds like your car needs to be given a good hard run to burn alota the crap out of the cat

if that doesnt work, start with the O2 sensors... then the cats... hopefully it wont need to go that far

 

Thanks carnal_c30,
I will try that first.

 

Go to a shady mechanic, and give some cash!

 

I would recomend an fuel system treatment, like valvoline synpower or a similar fuel injector cleaner. This costs about $3 a bottle and treats an entire tank of fuel, do it every 3,000 miles. If you put this in and run the tank to near dry, you might just pass emissions. Oil treatment is also recomended, such as "automotive restore" i usually do both oil and fuel treatment with every oil change.

 

You could try a solution called EMISSION PASS. ( Should be able to find it in any automotive store) You poor it into your gas tank with Premium gas and drive it for a couple of days it should help NOx to go down, and a oil change if you haven't already. Hope it helps.

 

Start with the O2 sensor and then the cats....those two usually fix emission probs.

If you're interesting in alternatives, put in a full tank of Chevron premium...the Techroline (sp?) is an effective detergent if you have carbon holding open your valves slightly.

 

ok here are some more detailed tips

if you use a fuel injector cleaner or fuel system cleaner DONT try to pass smog until you empty your tank and refill it and drive kinda hard on it- all the stuff you clean out from your injectors will need to be burned off, same if you clean your throttle body (a good idea for ya)

now if we wana get a little bit more exciting I would run one tank with premium (always do!) and a complete fuel system cleaner blah blah... empty the tank, and when I fill it again I'd put about 3-6 gallons of 100 or 106 octane NON LEADED racing gas in there, drive the car hard for atleast half an hour (cruise on the freeway at 80 or so, or with O/D off or in 4th gear) call the smog place and tell them you're coming in so when you arrive your car gets driven straight on the rack so it doesnt cool down

 

Make sure your EGR valve is clean. I got to find what we did to make the SC pass. Give me a sec.

 

Just a side note, but you should start up your car and let the engine run at least once a week.