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Old 11-07-2011, 02:28 AM   #1
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Default Po420-po430

Hey guys, got the ses light on codes are po420 and po430. Car starts and idles normally. but under acceleration i feel some hesitation but usually comes out of it in the higher rpms. could this hesitation be caused by bad cats? I have read alot on here about maf's being dirty/bad causing similar problems but the codes or po420 and po430. car doesnt fall on its face or anything but a noticeable hesitation is felt under acceleration. Car is 00 trans am m6 bone stock. im putting long tubes and ory soon but thought i would ask if hesitation could be related to po420 and po430 codes. thanks!
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Old 11-07-2011, 03:48 AM   #2
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Hey guys, got the ses light on codes are po420 and po430. Car starts and idles normally. but under acceleration i feel some hesitation but usually comes out of it in the higher rpms. could this hesitation be caused by bad cats? I have read alot on here about maf's being dirty/bad causing similar problems but the codes or po420 and po430. car doesnt fall on its face or anything but a noticeable hesitation is felt under acceleration. Car is 00 trans am m6 bone stock. im putting long tubes and ory soon but thought i would ask if hesitation could be related to po420 and po430 codes. thanks!
These codes are just for cat inefficiency, meaning that the cats are no longer scrubbing the exhaust properly. Not a big deal unless you have to pass a sniffer test.

Inefficient cats won't cause any hesitation or driveability issues at all, just incresed emissions which is what the codes directly indicate. On the other hand, if the cat material has melted or broken up and become clogged, that would certainly cause performance issues.

The fact that you mentioned this...

Quote:
but under acceleration i feel some hesitation but usually comes out of it in the higher rpms
...tells me that the cats are likely not causing the hesitation. If they were clogged, performance would get worse with more rpm, not begin to improve at higher rpms.

It never hurts to clean up the MAF. Lots of little issues have been traced back to dirty MAFs.
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Old 11-07-2011, 09:26 AM   #3
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Agreed, also consider possibly either a Dirty MAF, Bad Cats, OR o2's need replacement.

If the up stream and down stream do not jive, this is what triggers the code too. It could be due to clogged cats, or the sensors are going and are considered "lazy". Also driving WOT or part throttle can be effected and generally when the car goes to WOT its not looking at the o2 sensor reading so there should be no reduction in performance.

IMO I would consider if they are original is to replace all of them at the same time and clean the MAF, from there if no change, then its the CATS. It kinda sucks as one of the o2's are pretty far up there and you may have a better change removing the cat to get at it (free labor.... ) so you may just do it all at the same time.

Remember to clear the codes out with a scanner and do so many drive cycles to re set monitors incase you have a ODBII scanner emissions requirement.
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Old 11-08-2011, 12:32 AM   #4
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ok I'll just replace them all this weekend went ahead and got bosch o2s should be in tomorrow. if this doesnt get codes off then i wont be replacing the cats since i plan on putting some tsp long tubes on this winter with ory. One ? thought tonight i was driving home from work and i decided to lay in to it a little on the interstate and the ses light started blinking for a few secs. now i havent scanned codes yet but if i am not mistaken that is indicating a misfire correct? that would not have anything to do with 02's or cats would it? i wouldnt think so...but It got new wires and plugs 2 months ago. thanks for any input
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Old 11-08-2011, 07:23 AM   #5
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Flashing SES light does indicate a mis-fire. Which can cause O2 sensors to go out of wack as if one or more mis-fire the exhaust mixture will be different and can throw off the difference each O2 reads.

I would pull all the wires, plugs, re inspect, re gap, re install.

What plugs / wires did you go with??

Also to mention once you do the o2's IF there is an issue it takes so many drive cycles to reset the monitor so IF its going to throw a SES, it may not do it immediately. Just a FYI.

So if I was looking at this car, this would be my check list to start.

-Clean MAF
-Replace all o2 sensors
-R & R spark plugs and wires, inspect and decide what to do.
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Old 11-08-2011, 10:52 AM   #6
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my ses was flashing and turned out to be my o2 sensors. your problem sounds like o2 or maf. o2 sensors and a can of maf cleaner should do it. i have the 420 and 430 codes constantly thrown but that is because i have lt's and no cats.
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Old 11-08-2011, 12:15 PM   #7
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my ses was flashing and turned out to be my o2 sensors. your problem sounds like o2 or maf. o2 sensors and a can of maf cleaner should do it. i have the 420 and 430 codes constantly thrown but that is because i have lt's and no cats.
Exactly as if both CATs crapped out at the same time so as much as we can assume, generally both parts do no break at the exact same time, when it comes to sensors or CATs.
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Old 11-09-2011, 12:32 AM   #8
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i ordered the msd wires and ngk tr6 combo from texas speed think i paid around 80 bucks for them also got some lts and true dual exhaust. will my bosch 02s i just bought work with the lts ? and im deleting cats with lts and ory will i continue to throw light for cats or can a tuner take care of that? I am putting it on a dyno when this is finished because i have a torquer v3 going in as well and a ls6 intake. I will pick up a can of that maf cleaner from advanced and clean the maf. i know this is off subject but you guys think this is a good combo? already got the moser 9in coming and sub frame connectors. Car will never see track ever. Thanks a million guys for all the input.

those plugs and wires seem to do ok? anyone else running them?
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Old 11-10-2011, 03:30 AM   #9
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those plugs and wires seem to do ok? anyone else running them?
I would not use TR6s for a stock car. If you are spraying, boosted or have high compression than the TR6 would be a good choice, as they are a colder plug. For your setup, I'd go with TR55s.
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Old 11-10-2011, 10:54 PM   #10
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I would not use TR6s for a stock car. If you are spraying, boosted or have high compression than the TR6 would be a good choice, as they are a colder plug. For your setup, I'd go with TR55s.
Thanks, Ill change em.
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