annoying problem I need help
 

well last MONDAY my msd 6a box totally took a shit at he worst possible time on the highway, missed class, had to get towed , brother brought me my tools and fixed it in the parking lot and drove home, wasn’t fun

well here’s some notes and my problem

while the box was dying I drove really slow in the right lane for like a few minutes, the car was misfiring due to losing spark and the check engine light was flashing, I’m guessing this caused me to run really rich, I fixed it in the parking lot with a brand new OEM distributor cap and rotor (don’t ask) and the spark plugs were change 3 days before that (stock NGK), started the car perfectly fine no CEL or nothing


WENSDAY
check engine light P0420 / #67 Catalyst Efficiency Below Threshold, WTF!
now the check engine light has been coming on every other day since then, I clear it every time it comes on with my scanner, I pulled the battery to reset it didn’t help, the cel only seems to come one whenever I am just cruising at around 40-80mph with steady throttle, city driving doesn’t seem to set it off

I really stumped is it possible for the car to just get used to an ignition, its been on there for almost 2 years, now that its off making me run rich, or did running rich for that little amount of time destroy my cat or clogged and 02 sensor, as of right now I haven’t done anything I’m thinking about getting a new 02 sensor but I don’t think that will fix it because the code says the cat is fucked not the sensor HELP!!!

What year civic do you have? Is your cat gutted or stock? You have to understand that a catalyst code does not mean that your cat is bad. It will most likely mean that your O2 sensor is going bad. If you have an OBD2 civic (96 up), your primary O2 sensor calculates what's coming into your cat while the secondary O2 sensor calculates what is happening (or rather what is being processed in the cat based on what the primary O2 sensor initially read before hand. Any erroneous or insufficient calculations will toss a CEL. This CEL can also place your ECU on a limp mode. So, my suggestion is to either borrow or get another secondary O2 sensor to see if the same problem occurs.

Sounds like a bad O2 sensor[s] to me too... I had one go south on a domestic -- took several months to totally fail.

When it first started throwing CELs, it would only happen when I was pulling long hills with steady throttle. As soon as I topped the hill and backed off the throttle, everything was fine until the next time.

This happened more n' more, over probably 6 months, until I finally got tired of it and replaced the primary sensor -- end of problem.

its a 00 civic stock cat never touched, just bolt ons, never had this problem before it just happed when I took off the ignition

does anyone know where I can get denso 02 sensors like OEM ones for cheap with the harness or not dosn't really matter...

the primary and secondary sensors are the same exact kind right???

www.prostreetonline.com

http://www.prostreetonline.com/oem/q...tion=000633609

By part number they are different. I think it is because of that rubber grommet for the secondary. I have intechanged them before and worked fine with me.

thanks i'm gonna try it out Ill let you know how it goes

goodluck mang

I just bought this denso 02 sensor on ebay for $50 its a 4 wire universal, I dont mind connecting the wires to save $150+ this should be ok right ?????

http://cgi.ebay.com/ebaymotors/DENSO-O2-Oxygen-Sensor-Honda-Civic-Del-Sol-Integra-4Wir_W0QQitemZ8050887030QQcategoryZ33610QQssPageNa meZWDVWQQrdZ1QQcmdZViewItem

Good choice on the denso
I personally would have spent a few more bucks and gotten one with a plug, but no big deal. www.sparkplugs.com sells that kind (denso) for really good prices.

(oem sensors are denso)

well I changed the 02 sensor yesterday and the CEL came on again this afternoon same code, about 24 miles later while I was sluggin it through the rain in 5th gear, about 55mph, it seamed like it came on a little later but its not supossed to come on at all.
now what do I do, I'm thinking about changing the primary 02 sensor also....

Do that. If not, get an anti-foul or an O2 simulator. Remember what I mention up top, OBD2 uses both primary and secondary to calculate catalyst efficiency.

I bought a primary O2 sensor too, I'm waiting for it to come in the mail, anyway, I know this sounds extremely simple and theoretically is should work but I'm sure it been though of already and doesn't work.

what if you just put a resistor between the signal wire to reduce the voltage the ecu reads???

as long as you do not put it on the primary since pri O2 sensor is an input to your fuel calculation. You can simulate the secondary in a few different ways:
1. Get an anti foul plug
2. use an oscilating O2 simulator. You can even build your own. Check out the Step By Step forum.
3. Switch to OBD1 ECU

yea I built that 555 o2 simulator, but I dont know if I trust it on my car. If the new sensor doesnt work, how the hell did I fuck my car up?????

I just bought an 02 simulator for $30 off o2simulator.com, i'm going to put it on an oscilloscope in school just to see what the signal looks like, to bad I cant take one home to see what the fuck is going on with my car

I might try that step off thing too we'll see

my wonderful primary o2 sensor is seized on, i'm going to have to cut out the bung and weld in a new one tomorow YAY!