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so i just got a code reader and hooked it up to see what was up with my car, im getting misfire codes on cylinder 2 and 3, as well as a random misfire
the catalyst is performing below threshold, and im pretty convinced its 02 sensor issues. the problem is that i have no idea which of the 02 sensors it is.

any help would be apreciated!

anyone?

 
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if you didnt get an "02 sensor code"

I dont think its your 02 sensor.

 
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Dude, it is spark plugs, replace them and clear the code and you are golden. I just had that on my 02 Civic. Misfire on 1, 3, 4. New NGK plugs and she's running sweet.

 
Rep Power: 315

yep thats good advice^

 
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they are new plugs

i replaced the plugs, and i got a smell of gas when i ran the car the first few times. a few days later i tried again and the smell is gone this time. i have an actron code reader, and it did give me an 02 sensor code, but it didnt say which one.

edit: they are platinum NGK plugs btw

 
Rep Power: 813

well the emissions sensor doesnt really affect performance so im guessing its the primary that went bad (the one that calculates fuel mix).

 
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would you put money on that bet? coz it'll cost me $250 for the part

not that im going to hold u responsible btw.
the whole catalyst below threshold made me think the second 02 sensor was ok, coz it's working at least.

 
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well the code should tell you which sensor. get a $28 code reader from ebay, it tells you all of em.

 
Rep Power: 247

Yeh and on top of that the code itself should tell you wich one it is. Read the trouble code section and find wich one it is. I wont sticky it but you can find it!!!!!

 
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well the confusing thing is that it isn't telling me which 02 sensor is dead. my code reader is the Actron Pocket Scanner, and it just says "02 SENSOR" on the screen, it doesnt specify. none of the codes im getting are for the 02 sensor.
the scanner is shows the initial codes of the misfires and the catalyst issue, then giving me lines saying FUEL, EGR, COMP, and 02 SENSOR. i was letting it idle this morning, and the RPM's slowly drop until it's around 100-200 rpm and stalling, then it shoots up to about 1800 RPM, evens out around 1000, then slowly repeats.

 
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what are the actual number codes it gives you? forget about words. idle fluctuation is a sign of a dirty IAC valve on the throttle body or possibly even a tps sensor defect.

 
Rep Power: 315

yep sounds like a dirty IAC

 
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what does IAC stand for? im assuming thats the main valve in the throttle body i see when i remove the filterbox.

as for the codes... its quite a list actually. its a 1 line display on the code scanner, so some codes are multi-line. but here's the big list.

"9 CODES
P0420
P0302
P0303
P0304
P0300
MIL ON (manual says thats an emissions issue)
MONITORS
1 INC
EVAP
7 READY
MISFIRE
FUEL
COMP
CATALYST
02 SENSOR
02 HTR
EGR"

i then cleared the codes, and when i restarted i got this:

"5 CODES
P0420
P0302
PO303
PO300
PO420 PD"

 
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Wow!!!^

 
Rep Power: 247

Man, go to the dealer. Before your car craps out or ruins ECU

 
Rep Power: 425

The "Catalyst Under Threshold" thing is a disagreement between the primary and the secondary O2s. The values aren't matching and it thinks your car is running too dirty.
You can try changing both of them, but you may want to look up in the cat and see if there's anything in there, or if the brick is fried, etc...

"IAC" = Idle air control
But if the car is missing and ****, it may or may not be the source of the rough idle. It sounds like your car went to hell... and having someone look it over would probably be best. Thats a lot of problems to have all at once without wondering if there's something serously wrong under the hood that should be looked at very closely.

Below the line that says "MONITORS" on that list can be ignored... thats just the readiness monitors that the computer is putting out.... those aren't trouble codes.

 
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i brought the car into a mechanic at the start of all this, and they told me i had to change both 02 sensors because they work as a team so i need to replace them as a team, as well as a list of little things like injector cleaner for $7 and lucas oil additive and to change the plugs and the oil, and to clean the throttle body.

so i decided i didnt much like the sound of replacing 1 02 sensor because the OTHER 1 is broken. i was hoping i could track down which one was really the problem, and i've kinda lost faith in the mechanic. the original problem was that when i was driving down the street, the car just kinda bogged down. i would floor it and it would even out and be ok, but the revs weren't picking up like normal all the time. i think im just going to buy an 02 sensor, the primary one, and hope for the best. i really dont want to bring this to a mechanic again at this point. hopefully im not making a huge mistake!

 
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I was wondering if you had fixed the problem yet since my car is giving me the same codes and bogs down quite a bit also.

 
Rep Power: 247

I got 4 codes yesterday all random misfires on all 4 cyl. Dealer said it could of been bad gas too!!! Try some 93 to dilute your gas, i did codes went away! But still have a misfire here and there, sucks!!!! Taking it back, hopefully they will fix it for free, I'm broke...