sargentpilcher

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.

Short Version:
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 version 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.

Gunner

did they test it right after changing the injectors or did they wait for the ecu to relearn the new fuel ratio? if they were leaking then it was sending more than you needed... just wondering..

sargentpilcher

I don't think they waited, or at least they didn't mention it, but I've driven it probably 50 miles since they were replaced, and the car was still unsmoggable due to the speed surges. Do you think that's a long enough time?

Gunner

Hard to say you can try but here are the things to think about.

Test for DTS's (Diagnostic Trouble Codes): Might point you in the direction of whats wrong again..

Testing Fuel Pressure: Test for proper fuel pressure with a fuel pressure gauge. Connect the gauge to the test port on the fuel rail. Fuel pressure reading's vary depending on the system for the vehicle, most throttle body injection cars (TBI) are between 13 psi and 17 psi and most (DPI) direct port inject systems are between 40 psi and 55 psi..(dont remember yours off the top of my head)

Plugged Fuel Filter: A plugged fuel filter can cause an engine to surge. Proper fuel system pressure is critical to fuel injected engines, other wise there will be inconsistencies in performance. To check for this condition remove the fuel filter and inspect, replace with new unit and recheck system.

Check Engine for Vacuum Leaks: If an engine vacuum leak is present it will cause the sensor input readings to the PCM to be incorrect resulting in an engine surge.Inspect the air intake boot for tears and vacuum feed lines to all accessories.Also an IAC (Idle Air Control) valve bypass hose can develop tears/holes mid way through the hose, inspect thoroughly. Sometimes a vacuum leak can be detected by opening the hood, start the engine and allow to idle, listen for an audible whistling sound. Inspect that area of the engine compartment to locate the leak

Check for Plugged Exhaust System: The exhaust system in your vehicle is designed to release exhaust gases from the engine to the rear of the car. This system is designed to have about 3 pounds of exhaust backpressure under full throttle. This means the engine should not have to push more than 3 pounds of pressure to release the exhaust at any given time. If a catalytic converter plugs or breaks apart it will plug the exhaust system causing an engine surge.

Test for Weak Ignition Spark or Failing System: A weak ignition system can be a sign of a failing ignition component and can cause the engine to surge.

Check for Standard Transmission Clutch Slippage: When a clutch assembly starts to wear it can cause an engine surge sensation

A lot to look for but HTH

sargentpilcher

Thank you so much for your expertise. I will definitely be taking my car to a different mechanic to see what they say.