emilyejj

I have a 2004 Honda Civic EX Coupe, 1.7 VTEC, manual transmission with almost 138,000 miles.
About a month ago, at the beginning of my drive from California to Texas, my car broke down for the first time ever, which turned out to be a bad fuel pump. I got that replaced. Then, a few hours after that, both my check engine light, code P0420, and battery light came on. Turned out the alternator was shot. Got that replaced. The battery light went off after that, but the check engine light stayed on. Once we got to Texas I got the light reset, and it came back on a few days later. I was then told to replace my catalytic converter. I bought a cat from a parts store, which was a direct fit. I then decided to just go ahead and replace the downstream O2 sensor as well, due to the fact that I had already replaced the upstream a few years before, and it might be time to change it out.
As for performance issues, following the fuel pump replacement, my acceleration was crap. It was never phenomenal to begin with, but it worked just fine for me, until we replaced the fuel pump. Getting up to speed was a feat. Also, the car seemed to get these little bursts of power, where I'd be at a steady speed and all of a sudden the car would accelerate a little bit more, and then go back to normal.
I finally had the cat and O2 sensor replaced, and a day later, the check engine light came back on. However, the acceleration is much, much better, but it still seems to get those little bursts of power. Does anyone have any idea what the issue could be or what I should do?

ezone

1) Aftermarket cat is always suspect.

2) Let's assume for just a second that your cat was a decent quality replacement (Was it a CARB approved/certified unit?):
A perfectly good cat can be ruined in a matter of only seconds when under adverse running conditions. Misfires, rich, or lean can all trash a cat in a hurry. Your performance issues could easily have done the damage.

emilyejj

It says it is not CARB compliant. It's a Walker cat, Direct Fit for OBDII vehicles. Anyway, another twist, I just went back up to AutoZone to have the check engine light checked again, and now, not only do I still have P0420, but I also have P0134, which is tied to the O2 sensors. They also said the two can go off simultaneously for the same reason. Maybe the mechanic who installed the cat yesterday screwed something up with the O2 sensors? He replaced the downstream sensor, and just removed and reinstalled the upstream

ezone

Ok, that's a mediocre cat in my book and would be immediately suspect, even without a known poor running/poor performance problem.

Anyway.....

P0134: A/F sensor no activity detected. That's the front sensor. (Is it properly connected? Is it physically damaged? IIRC on some of these it is easy to damage it.)

This P0134 code canNOT be set at the same time as a cat code. (If those guys at the Zoo could actually FIX cars, do you really think they would be schlepping parts? Guess who makes commission on selling you all those low quality parts...)

The codes may have been retrieved at the same time, that does not mean they were set at the same time.

This P0134 code will prohibit a cat code from being detected because the cat monitor is suspended from running as long as this sensor fault is present. There are several codes that will stop the cat monitor from running. If you retrieved a cat code, then it had to be present prior to the A/F sensor code.

FYI, here's a quick list of some of the codes/systems that will stop the cat monitor (P0420 code self test) from running:
ECM/PCM
A/F sensor
A/F sensor heater
secondary O2
secondary O2 heater
MAP
ECT
IAT
EGR
BARO
VSS
VTEC System
Fuel System
Misfire
EVAP



I suppose you don't have OEM A/F and O2 sensors either?

emilyejj

No, those aren't either. I've replaced a lot of stuff on this car with only aftermarket parts

emilyejj

I'll go look at them tomorrow. It's a bit too dark to do it tonight

ezone

I have one of these at work...



It will install almost all of the smaller cheapo parts into the dumpster with amazing speed and accuracy.
Bosch Platinum spark plugs make some cool noises as they fly too.

dutto

Aftermarket Cats do Not have the same threshold of ULEV as factory honda does, Hence the light returns shortley after replacing CAT Conv. if you want it to go away install Anti-foul plug adapter. Works like a charm
02 civic 328,000

Bricktop ivi

hahahaha

Oh man, i haven't seen one of those in years!