Agent_EM1

Alright, so I traded my bone stock 96 Civic CX Hatch for a 1997 HOnda Civic LX Sedan. Why a Sedan? Because i'm a big fella with a family and felt the 4 doors would be more convenient. Anyways, about the car...

I have a 97 4dr Civic LX w/ a stock LX motor. The car is pretty bad and far worse than I was told it would be. For now, i'm just trying to pass emissions. I went to DEQ (Emissions Testing in Oregon) on Thursday and failed due to a bad MAP Sensor. I replaced my MAP Sensor twice as I thought the one from Schucks was faulty. I am now using an Autolite Map Sensor from Autozone and I reset my ECU several times and i'm still stuck with a check engine light.

How did I reset the ECU? The first time, I pulled the ECU fuse, and removed the Positive terminal for an hour while I was at work. The Second time, I completely disconnected the battery. I still have the check engine light.

Now, let me tell you all about my car so maybe you could help me out. The previous owner put a straight through exhaust that was shitty. It went straight from the headers with no catalytic converter to a glasspack with a huge TIP. Yes, a tip! No muffler, no resonator, just a glass pack welded to a very large ricer TIP. The headers on the motor appear to be DC Ceramic headers and are 2-piece. There is an O2 sensor connected to the DC headers.

First things I did were have an exhaust shop chop off the glasspack and put on an OEM muffler and a Universal Catalytic Converter. Could it be the Catalytic Converter? I still have the stock headers that are connected to the stock catalytic converter.

I just want to pass emissions. Any help is GLADLY appreciated as I just want a normal running car for my family to use.

IhateworkingoncaRs

Your car should have 2 o2 sensors. One before and after the cat. If your missing one, that will cause your check engine light to come on. However, that alone will not cause your emissions to fail, but the only way to know if your cat is working properly is to be able to moniter both o2 sensors. I don't live in a emissions state so I don't know how the state does it but in school, we stuck what the teacher called the "sniffer" into the tail pipe and got a few readings in PPM (parts per million) on a computer screen. Now, if you can post up a picture of your PPM readings, I can help out more. As far as your map sensor goes, getting 2 defective parts in a row is pretty slim so I'd start looking at something else. Also, did the code relate to the map sensor?

Agent_EM1

THank you. Yeah, the code was for the MAP sensor. I got it checked by 3 different mechanics, and through Autozone. One mechanic charged me $160 to take out my MAP and replace it with a new one. I bought the MAP myself for $58 and changed it myself. Anyways, looking at my headers and exhaust, I have one O2 sensor going to the headers, and one after the headers on the "2-1" pipe, about a foot away from the catalytic converters. The DC Headers are 4-2-1 headers.... Then underneathe car, below about where the firewall is at, lies my catalytic converter. SO the 2nd O2 sensor should be after my catalytic converter?

wrenchez81

yeah bbuut if the engine stalls while the key is in the on position it can cause you to get a map code!!!

IhateworkingoncaRs

Yeah, the 2nd o2 sensor should be after your cat. I bet that is whats causing the computer to throw the map code. The 2nd o2 sensor's job is to read the exhaust once it's been through the cat and the computer will compare it to the first o2 sensor and other sensor readings and it can determine if something is wrong with the air and fuel mixture, bad cat, or bad sensors. In your case, the computer is probably super confused because the readings from the first o2 sensor is identical to the 2nd o2 sensor because the mixture has not pass through the cat yet, and out of randomness, it throws the map code which would explain why your code still exist after replacing the sensor. We all want to believe that computers know everything but truth is, we have to be smarter than the computer . I hope this helps.

Agent_EM1

So what's your best advice? Should I just get my stock headers/cat installed? What happens if I have 2 catalytic converters? Man, this is gonna get expensive. COuld I get my o2 extended to after my catalytic converter?

IhateworkingoncaRs

You can have a shop weld a o2 bong behind your cat and install your 2nd o2 sensor there and just plug up the whole with a bolt. Your check engine light will probably go away and it might make your emissions reading correct. However, your universal cat still might be a problem but with the o2 sensor in the correct spot, a shop can moniter your cat for you.

freakasis

trace the 3 wires from the map all the way back, i bet you find a short or loose connection. if it was modified he may have had a AFC in there and would have tapped into the map signal wire. prolly under the dash near the ecu, pull the carpet back on the pass. side and follow the wires up to the firewall and see if anythings hacked up.