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Guest Message by DevFuse

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BRAT still failing smog...... possible CARB rebuild

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4 replies to this topic

#1 s'ko



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Posted 07 June 2005 - 03:40 PM

So BRAT continues to fail smog.

CO levels are through the roof. New O2 sensor and cat were installed. Car is tuned and idles beautifully. Revving the engine w/o load gets low CO levels. Running the car on the dyno (underload) makes high CO levels. One thing that makes me think it's the carb is b/c even with the fuel mixture screw turned in all the way, it's running rich. That's not normal right?
Someone mentioned that the EGR system might be clogged. Anyone have any insight on getting to it? Will seafoam clean that up?

Anyone have problems that I am having?

Thanks for the help

#2 BoostedBalls


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Posted 07 June 2005 - 05:05 PM

A couple ideas,

even with a new 02 sensor, make sure the threads are clean with a thin layer of silver anti-seize, make sure the exhaust pipe has a good ground.

Get a leak-down tester, if it says you are running rich even with the screws all the way in, you may be blowing a little oil past the rings causing the reading to "look" rich.

Might run 2 cans of B-12 through the tank when you are about empty, works great for cleaning the inside of the carb.

Pull the PCV palve out and shoot some carb cleaner through it.

I'm a little worried about your rings if levels are only high under load. I would probably drain the oil and fill with 50W oil. That will reduce the amount of oil slipping past the rings.

You might step up to a hotter thermostat, just for the test.

Good luck!

#3 Camelwagon


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Posted 30 August 2005 - 02:29 PM

So by "turned in" do you mean to turned clockwise to the right?

#4 subarunuts


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Posted 31 August 2005 - 12:22 AM

Sometimes running out of spec for a long period of time will kill the cat - there may not be anything to do but weld in another cat - make sure the AIS is working properly - rather than replacing the cat that's in the y-pipe it may be simpler to add a second one farther back where the resonator is. Vacuum leaks are very common - check the EGR system as it will activate under load at speed.

In order to pass mine, I replaced the y-pipe with a lower mileage one with a better cat, and re-routed the entire vacuum system using new hose and bypassing some of the less needed components that looked suspect. I bypassed all the hard lines and simplified much of the routing. Some knowledge of the principles of operation of carb emissions gear is needed, but it's not difficult to figure out. Most of the stuff in there is "passive" for trapping rougue gasses when your rig is sitting in a hot parking lot - this stuff can't be tested other than to look under the hood to see if it's physically present - no tailpipe test will show any difference with or without it. Even in CA.

#5 monstaru


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Posted 31 August 2005 - 07:42 AM

i was running a little rich as well.still don''t know why, but when i rebuilt my carb it was a lot better .our laws are not as stringent up here , but are getting that way.if you need to check your egr valve take it all the way off,that way you can see the backside and be able to thouroghly clean it . i used carb cleaner.it seemed to work .and if you tackle your carb yourself just be patient with yourself and put everything in sight.you don't want to be stepping away from the project to grab things.it is easy to get lost ,if you have never done it before.try to do it all in one sitting.

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