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Failed smog

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Old 09-01-15, 03:46 PM   #1
LEX_GS4
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Default Failed smog



I failed smog today, I have a 1999 Gs400 with about 230k original cats, I'm thinking cats but just wanted to make sure.
The motor has been completely rebuilt around 200k (Rings, bearings, headgasket, timing belt, plugs)
Have been throwing codes for p0430 and sometimes p0420 for cats. And ideas?
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Old 09-01-15, 05:28 PM   #2
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you clean your maf?
change 02's?
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Old 09-01-15, 06:07 PM   #3
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check the flange gaskets after the cat first... that is what is tripping my occasional CEL... and i'm due for inspection this month...

i have already ordered new gaskets...
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Old 09-01-15, 06:24 PM   #4
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I've changed my AF sensors not o2's and I think that wouldn't effect my smog as much..
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Old 02-12-16, 03:05 PM   #5
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Did you manage to get your car past smog? I barely squeaked by in my smog test today but next year I wont make it. Just wondering what you replaced and how much it cost
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Old 02-12-16, 05:19 PM   #6
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I had similar results when I passed my last smog check. One number was right on the max. They told me I wouldn't pass the next time. Then I found my results from 2 years before and I was right on the max also. I've been told driving for a while before testing also helps. Like a 30 + minute trip. I think I drove for about 45 min.
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Old 02-12-16, 06:58 PM   #7
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Hopefully I pass next time then haha. The guy mentioned driving more before hand too. He said i should go for an hour and try an octane booster. I do get random codes for my cat being inefficient, so im really hoping to dodge that cost
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Old 02-13-16, 08:37 PM   #8
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High Hydro Carbons(HC) are due to unburned fuel. What helps burn fuel? Coils, spark plugs, plug wires.

How is your car running? Is it missing(misfiring)? When was the last time you had it tuned up? Try a tune up first, if that doesnt work your Catalytic converter must be bad. Have you ever replaced your converter? If its the original, it may be time to be replaced.
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Old 02-14-16, 03:21 PM   #9
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Its running pretty good for 250k miles. No misfires but the idle is a little rough (ive done everything i can to try to fix it, clean tb, replace spark plugs, clear ecu, etc). I think its either a small vacuum leak somewhere or something with the ecu. I think it could possibly be the ecu because it behaves nice for a week or so after an ecu clear then goes back to being a little rough. But I also I think it could be a vacuum leak because it "surges" +/-100 rpm sometimes at idle and more often on an incline.

The cats are original and the spark plugs are NGK iridiums and have about 50K on them. I had a tune up a few weeks ago (oil change, fuel system cleaner, air filter) when i changed out the drivers side spark plug tube gaskets and valve cover gasket.
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Old 02-17-16, 04:38 PM   #10
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Definitely it could be a small vacuum leak if your idle jumps around, but if there was your ECU should throw a code for system too lean. I would double check your vacuum lines, use soap/water in a spray bottle to help see if there are any bubbles forming. If there is, you found your vacuum leak, if not I would take the 400 to a muffler shop and ask them to do some tests on your Catalytic converters to see which one is bad. I believe the 400 have 4 cats? Cats are pricey so make sure you only replace the defective one. You dont need to replace them all
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Old 02-17-16, 09:00 PM   #11
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Thanks for the advice! I will definitely use the soapy water this weekend. Yesterday I went poking around and pulled the spark plugs on the drivers side. I think I will replace them soon as they weren't in as good of shape as I thought they should be. Im pretty sure there are 4 cats and last i checked they were 1500 each
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Old 02-17-16, 10:22 PM   #12
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How would you get bubbles with a vacuum leak?
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Old 02-18-16, 02:25 AM   #13
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Quote:
Originally Posted by bruceb58 View Post
How would you get bubbles with a vacuum leak?
I was wrong about the soap and water checking for vacuum. Thanks for questioning that. You wont get any bubbles because you would need PRESSURE. Soap/water is a good tool to test for a pressure leak(small tire leak). But when you spray soap/water on a vacuum leak, the idle will change slightly. Best thing to do for vacuum leaks is perform a smoke test.

Youtube - Smoke test, soap water vacuum leak test, this dude makes his own smoke tester tool out of a Gatorade bottle, some vacuum lines, vacuum tees and a pump but I wouldnt recommend it. It almost look like he didn't have the smoke-small fire contained. It worked, Im sure he performed this several times but me personally, I wouldn't mess with fire around a vehicle, so much can go so wrong.
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Old 02-19-16, 01:53 PM   #14
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Default Smog check

Quote:
Originally Posted by LEX_GS4 View Post


I failed smog today, I have a 1999 Gs400 with about 230k original cats, I'm thinking cats but just wanted to make sure.
The motor has been completely rebuilt around 200k (Rings, bearings, headgasket, timing belt, plugs)
Have been throwing codes for p0430 and sometimes p0420 for cats. And ideas?
First the basics... get a tune up, change the oil and filter and use the highest octane you can find.......... I have 239K on my car... it passed at 200.... he said I'll need a low milage car used catalytic converter next time.... he said that they are easy to get
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Old 02-19-16, 02:01 PM   #15
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Default Smog

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Originally Posted by LEX_GS4 View Post


I failed smog today, I have a 1999 Gs400 with about 230k original cats, I'm thinking cats but just wanted to make sure.
The motor has been completely rebuilt around 200k (Rings, bearings, headgasket, timing belt, plugs)
Have been throwing codes for p0430 and sometimes p0420 for cats. And ideas?
During my tune up, he said I had some clogged injectors and he put in some used ones.... ran like a charm and passed... but again... we get smogged every 2 years in SCal... he noted that he would have to install a used catalytic converter next time... will do... I have a 1999 Lexus 400gs.. and a use 2008 Lexus 350 GS.... I wanted a 460 GS but would have to travel 1000 miles to find one listed on auto trader... the 350 is more or a luxury car with more bells and whistles, but the 8 cylinder 400GS is a racing car. These 300 series BMW's and such, gas it in neutral for a race and I just laugh.. the car's top end is 152 according to a car buff and was the fastest production car for it's price. BMW's, Mercedes, Audi, ect... still love driving the old car the best....
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