I have a 97' Honda Civic DX Manual Transmission. The last few months have been a nightmare situation for me, and I'm about 1,200$ deep in repair costs already, and I want to be sure before spending any more money on the problem.

So basically what my mechanic is saying is that my car is unsmoggable because he cannot maintain speed as he's testing it on the dynometer. That is to say, he has to maintain a speed of 15 MPH for 30 seconds, and then again he has to maintain 25 MPH for 30 seconds, but my car will jump in speed and surge, which cancels the test out and makes him have to start over.

The reason he says is that the onboard computer on the car is lazy when receiving signals from the oxygen sensor. The oxygen sensor will send the signal to the computer about what the fuel/air ratio should be, and when the computer responds it surges the fuel ratio and makes the car speed up during the test, which makes it fail.

He wasn't able to give me an estimate on the costs of repair because he didn't know how much it would cost. Does anybody have any clue how accurate what he is saying is? And if there is at all a possible DIY solution?

Long story for full background of the car troubles:
I needed a smog test done, but my check engine light was on. I got a OBDII sensor module to scan the codes myself, and it came up as a bad 02 sensor/catalytic converter. I bought a new Cat, and 2 new 02 sensors, and replaced them myself.

Then, in January, I took my car to be smogged, but the place I took it to said he couldn't do it because of the above mentioned reason of my car being unable to maintain a speed. He made about 4 attempts before giving up.
Now me, wanting a second opinion, took it to another smog test place, and they too turned my car away because they were unable to smog it.

I then took it to a 3rd place, Quality auto care. I informed them of the problem to try and start getting it fixed, but they found a workaround, by attaching chains to my car for safety, and one of the mechanics would hold in the throttle position sensor, while another mechanic performed the test, and they were able to test my car, and I failed miserably. They slowly replaced parts, they said my Cat was fine, but found a bad 02 sensor, so they replaced it. That brought my numbers down, but I still failed. Upon more diagnostics, they found my fuel injectors were leaking. They replaced my fuel injectors, but this time they were not able to smog it, because of the fact that my car will not maintain speed.

Well I didn't mention before, but I had qualified for the CAP program, which is basically financial assistance through the state for emissions repairs. Because I had done that, he recommended I take it to a referee station to try and get a waiver because of all the work that had been done on it. So I took it to the referee station, and he said I qualify for a waiver on the smog test, but he can't grant me a waiver without being able to smog my car first.

So I can't get a waiver and register my car until I get this fixed. I'm all out of money, and am having to turn to my parents to help me finish getting it fixed. Please somebody help me out here.

 

I assume that you have the same problem trying to maintain speed on a level road. You have to fix that first. Whenever there's some obvious driveability problem there's almost certain to be smog too.

The theory about the oxygen sensor though makes no sense to me. I'd be thinking fuel pressure, throttle position sensor, throttle cable etc.

 

I've never noticed a problem while driving it maintaining speed, but I've never actively attempted to maintain a speed exactly for any period of time because it's pointless.

Originally the mechanic said my throttle cable was loose, but he tightened it, which helped a tiny amount, and the referee station guy said he checked the throttle cable and it was tight. Of course that doesn't mean there's not a malfunction, but the fact that you think the 02 sensor doesn't make any sense makes me want to get this problem fixed somewhere else.