[Eric]

I know this is old but ive been having this issue with my 2000 civic LX D16Y7 basic bone stock didnt even change the radio daily driver. I had this car for 10 years and this and the dreaded P1457 code that plagues all 6th gens is the only issues. I narrowed it down to something to do with emissions test the ECU does maybe. About 2 years ago the exhaust was just done and we put on a cat-less ebay stainless and it fit perfect. Aside from now getting a P4020? catalyst efficiency below threshold. I noticed the converter was cracked all the way down to the sensor. You have to take the cover off to see but inspect that before you move on. This can allow air and contamination into the upstream and downstream O2 and cause all kinds of surging and “loading up” the system. I noticed that when its doing that black smoke comes out of the exhaust and with the look of O2 data off a Solus tool told me that its running ridiculously rich. The sensor is flooded and the ECU freaks cutting off fuel to the system causing it to lean out. I observed this activity numerous times over the years and figured it was caused by the system failing some readiness monitors. Including the one that checks for catalyst. Without MODE 6 and even if the ECU’s diagnostic system may be too basic to tell which part of the tests its doing. I found a write-up on general EPA guidelines on how a car should check its catalyst. It, at random times, when all conditions are met(temp, drive cycle, etc) readiness monitor starts to dump raw fuel into the converter which causes it to “flash off” and cause a vortex that will pull the unspent fuel out of the cylinders rapidly so it doesn’t foul the EGR and spark plugs. It does this to see if you arent using a fouler on the downstream O2. The converter will burn off this fuel rapidly and it destroys and unnecessarily heats up the converter. This causes the crack if you were to drive through water puddle or get water down onto the really smoking hot converter. Under normal conditions the engine keeps the catalyst cool and burns off unspent NOX with the EGR and no problems should be had with this type of converter. I cant tell if this is my exact cause but I do see on a scantool it loads up a lot of fuel for a few seconds and then if you have a cat-less pipe it will foul the sensors and could foul your plugs. I fouled several sets of plugs and it leaving me stranded a couple of times because I didnt want to be a douche bag and stomping on the gas pedal. This is the only way you can overcome this issue is by revving your car all the way out and race it down the road at break neck speeds. Its not the best way and illegal but it keeps you from stalling and fouling plugs and possibly the EGR. My mileage since went from 34 to 30-32 which isnt entirely bad but if you unplug the battery and let it reset and start back up leave the fuel tank over half full(one of the conditions to set the readiness monitors is less than half tank of gas) and the engine light wont come on and it goes back to 34. If it does, it will start going into some kind of tamper deal and cause the engine to dump a large amount of fuel into your cylinders. This also causes the oil to go bad fast. I had 10,000 mile full synthetic smell like raw gas in about 3000 miles if the engine light comes on. Mind you the only codes on my car and I have to check it regularly because of the stupid EPA(dont blame them for reducing pollution) keeps me from being able to tell if there is a real issue. It will throw a P1457(EVAP Control leak tank side) and with no cat a P4020 (Catalyst Efficiency below threshold). I hope someone really has a good scientific write-up and can maybe decode the ECU readiness monitor on 6th gens. This gets annoying and seems to keep doing it regardless of what you replace. I never had any issue with sensors and injectors going bad. I have a bone stock weak LX that has been plagued with emissions problems. Honda makes a good car and is forced to botch it up with EPA emissions control. Im not trying to knock on the EPA but damn, how many cars are plagued with emissions issues. Luckily I live in Michigan and we dont test for anything because this car would have been shipped down the road a sold. I had already replaced the Evap vent shut solenoid that stays open for a vent but then shuts it to do a test. This causes road grime to enter the solenoid causing it to fail. Then you have a huge entanglement of hoses and tubes that crack and go bad. Then you can have issues with your charcoal canister saturating from something else going crappy on you. Then the entire EGR/Catalyst system is a botch job. Great engines, great cars, good bodies that dont normally rust until after 200,000 miles but cant keep the engine light off. Mine has been on and off now constantly staying on after not caring about the evap or catalyst. Normally runs like a top until it wants to do that test. Thanks for reading my input

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