View original topic: Carbon Build Up and Failed Smog Test Question
Vespagetti Thu Feb 02, 2006 7:23 pm

I have a perfect running '88 GL. It's a happy purring, never over heating, never smoking, immaculately maintained van with 77k miles on the clock. It just failed the smog test (NOx) by a narrow margin. :(

Has anybody ran a Carbon clean up solution thru the engine? Any tips?

I've been driving mainly around town, start-stop kinda traffic, no freeway driving or very little. So I'm hoping that it's a carbon build up that's causing this....

Thanks in advance.

msinabottle Thu Feb 02, 2006 11:16 pm

That will, they claim, remove carbon from the upper engine. I ran 3/4 of a tank with that in it through Winston and he sailed through emissions.

I don't know about motor-vacs and boxer engines, interestting question. I have used BG MOA in Winston's oil and BG Quick Clean. Got some real black gunk out of the engine. He's purring. That much, I know.


Vespagetti Thu Feb 02, 2006 11:44 pm

That's what I was looking for. Thanks!

At the risk of sounding stupid ...... are you supposed to drive around with this stuff in your oil and gas or just let it idle for a certain period? :shrug:

msinabottle Thu Feb 02, 2006 11:53 pm

With the BG-44K is put in around 15 gallons of gas, run it through, then add new gas, drive that a bit, to get the rest of the gunk loosened, and then you could try emissions.

The BG 'Quick Clean' you use right before an oil change--as in, minutes before. The BG MOA you run through an entire oil cycle, and drain it out with the oil. All these products are well regarded enough to justify their horrific prices--find whoever prides themselves on a low price for BG stuff.

I've had aircraft experts preach the virtue of Chevron Techron fuel injector cleaner, which has aircraft-grade Stoddard solvent in it. Prices on THAT vary widly, Wal-Mart has been way low. But I'd go for BG-44K in your situation. It's actually cheaper in the long run than the repairs it could prevent.

Best of luck!

Vespagetti Fri Feb 03, 2006 11:20 am

Thanks a million! Great info as always. :D

r39o Fri Feb 03, 2006 12:11 pm

Having gone through this in San Diego a few times now, I might be able to offer a suggestion.

Firstly, typically, no matter what you pour down the gullet of your car, not much change will occor, I have found.

Now on to the real solution:

*IF* your HC or CO is way low, adjust your mixture so they are in the normal range. Your NOX will come down, some.

If your HC and CO are within range, you may be able to diddle them a little and squeak past the NOX. BUT, typically, what you need is a NEW catalytic converter to bring that NOX down in an otherwise correctly tuned car.

DO NOT JUST WELD A CAT IN. Your are asking for problems later. If you are dealing with this yourself, go to Inter Auto Parts in Kearny Mesa and see if they have a cat. Cheapest in town. Or go to Vee Parts in National City or El Cajon. Techtonics may have a cat too, mail order.

If need your van repaired, I go to Wolf's on Engineer Road at Convoy in Kearny Mesa. There are a couple of other places in town too. Peanuts in La Mesa comes to mind.

Good Luck,

Vespagetti Fri Feb 03, 2006 11:22 pm

Walt, thanks for the info. I'm actually in Oceanside, I know Wolf's is a good place. I normally go to B&R Buggies up here for little stuff but they don't want to touch it this time (air cooled fanatics, heh).

Anyways, my HC is 69 (Max 121) and CO .45 (Max .70) still quite above average....

My NO is only about 140 over so adjusting the mixture may do the trick, no?

I kinda don't want to admit to myself that it's a CAT but maybe it's time to face the reality.

Thanks again....

r39o Sat Feb 04, 2006 10:03 am

Oh, OK. Go to Hugo's on PCH and Encinitas Blvd. Very good, too.

The cat is no big deal, actually. Once (if!) you get the bolts out, it is a simple matter to replace it. Good time to just stick in a new O2 sensor, too.

Cost: $150 for the cat and like $18 for the O2 sensor, good guy price last time I bought them.

r39o Sat Feb 04, 2006 10:04 am

Oh ya, and like I stated, you can diddle with the mitxture and see what the NOX does. Many shops do not have the correct analyser for that, though.

Phil G Sat Feb 04, 2006 10:49 pm

Walt was probably more on the money his first post - the cat. Look at the averages given on your test sheet. All your critical emissions values are way too dirty, and you have very low miles. It would have been helpful to know the Co and Co2 readings on the left hand side of your test page as that will tell much about the condition of the cat. But Nox is probably high because the first stage of the cat is gone (lost most of it's catalyzing Rhodium wash) and the second stage which operates at a higher temperature (the oxidizer) is gone as well and so the other gases are hi ppm too.
If Idle is fine you have no adjustments to be concerned about. Your car runs nice, so there's nothing in the fuel system to be concerned about. You can however do a few additional things to help you once the cat is replaced, and if it is original it certainly is time for that. Replacing Ox sensor is fine but will not make much of a difference. Unplugged, you're in open loop and I've seen the readings - not different enough under the test conditions to be what you are looking for. You can make sure your ignition wires, cap, and rotor are fresh, and your air filter is clean. You can also change your oil prior to the test and then drive the vehicle for at least 20 minutes to warm it up well, preferably on a freeway at speed, and deliver the car to the smog inspection and leave it running to keep the cat hot.

To understand the 3-way cat, here's someone else's primer . . . my fingers are feeling lazy tonight :D

Good luck

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