I have a 2000 civic with a 98 hx engine with a 5 speed tranny in it. When I originally bought the car, this setup was already installed.

I've done a few mods to it since I bought it, but nothing major. I replaced the exhaust manifold with a stock y8 manifold, installed a new high flow catalytic convertor and Greddy Evo2 cat back exhaust. I extended the wiring for the 5-wire o2 sensor, then discovered it had an ecu from an ex (p2p) in it. It was throwing a couple codes that I didn't know about because the previous owner had pulled the cel bulb. I bought an hx ecu (p2n) and all the codes cleared themselves.

The car was getting crazy mileage, around 47 for combined city/highway driving. A couple weeks ago, it threw a code for the LAF sensor. I did some research on H-T and found out that it was the primary o2 sensor. I found one and ordered it to replace it while still driving the car with the cel light for the LAF. The fuel mileage went down considerably, but we had to keep driving it.

About a week ago, it started running really bad. My son said it was idling funny and stalling on him. I had him park it at Grampas house until I could get there. I cleaned the IACV, reinstalled and started it up. It seemed to idle like it is supposed to idle. We jumped in a took it for a spin and 200 feet later it started to spit, sputter, jump and lurch. It had no power at all and wouldn't run at a constant speed. You had to mash the throttle to get it to barely accelerate. I turned around and parked it. The only code it was throwing was still the LAF sensor.

The next day, I went and replaced the p2n ecu with the p2p ecu it came with thinking maybe the ecu had fried. I then bought an p2n ecu from a guy on H-T who said it was working when he took it out. I put it in and it ran the same as it did when it started running crappy. I put the p2p back in and it is currently throwing a code for the primary o2 sensor and knock sensor.

I need to know what the hell is wrong with it. The only difference that I know of between the ex and hx ecu is that the hx has an egr valve, 5-wire o2 sensor, LAF from the 5-wire, does not have a knock sensor and the v-tec is controlled at different rpms.

Could a bad egr valve cause my problems? Can the o2 sensor be bad and causing my problems?

EE_Chris, lets hear what you think?

 

I'm right there with you with the bad O2 sensor (it'll be here in an hour in the mail), it will cause that issue. I near stalled at a red light, hit 500 rpm, and had to compensate with a bit of throttle. The car doesn't know how much fuel to add, as it's getting no feedback from the exhaust, so yeah. I've had rough idle, no power, etc.

Also, unrelated but the knock sensor code is due to the D16Y5 (HX) not even having a knock sensor, just the Y8 (EX/p2p), but you may already be aware of that.

 

THanks for the reply. I knew about the knock sensor issue between the hx and ex, I just didn't know if a bad o2 sensor could cause it to run that badly. Its been cold as hell and I really didn't want to crawl under it until it warmed up. It snowed about 6 inches again this weekend, Global warming? I was curious if an egr valve that is faulty could cause this also?

 

Ah could be, but if o2 is for sure bad then that's most likely it. I don't know why EGRs go bad so often... Glad my '96 doesn't have one.

Under the car, eh? I wasn't aware it was the secondary o2 sensor. Usually rough idle like that is caused by sensor 1 adjusting fuel/air ratio (in the header), and sensor 2 tells you if the cat's dead. Did the code say it was the sensor after the cat?
(Also, does HX even have two o2 sensors? I could be mistaken.)

Edit:
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I don't think you'll get any more useful replies.


Modified by Davus at 4:08 AM 4/30/2008

 

The primary o2 sensor is located in the y-pipe of the exhaust manifold that I got from an ex. It's not very far from the cat. The original hx manifold had the cat bolted to it in the front of the engine. I put a new cat on and have the secondaty o2 in it. I also have to extend the primary o2 wires so it will reach the new location in the rear of the exhaust header.

 

Bump for EE_Chris to reply

 

Where are all the y5 experts?

 

Bump for some more thoughts

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Davus &raquo;</TD></TR><TR><TD CLASS="quote">Ah could be, but if o2 is for sure bad then that's most likely it. I don't know why EGRs go bad so often... Glad my '96 doesn't have one.

Under the car, eh? I wasn't aware it was the secondary o2 sensor. Usually rough idle like that is caused by sensor 1 adjusting fuel/air ratio (in the header), and sensor 2 tells you if the cat's dead. Did the code say it was the sensor after the cat?
(Also, does HX even have two o2 sensors? I could be mistaken.)

Edit:
vvvvv
I don't think you'll get any more useful replies.


Modified by Davus at 4:08 AM 4/30/2008</TD></TR></TABLE>

Well, I finally got to changing out the 5-wire oxygen sensor in the car and now she runs smooth again with no cel's. Thanks for your response, I appreciate it.