Hi Guys,

Well I need some mechanical help, not sure which fourm to post it in so am sorry if this is the wrong fourm. [&:]

My theory is 2000 Civic DX (auto) is running rich (after a failed attempt at modifying the car).

In Jan 2007, I had the headers done, got a high flow cat installed and performace muffler installed. The mechanic reused my old oxygen sensors and extended the wiring harness from the orignal location (behind the rad) all the way down tot he new position just past the oil pan.

Right from the get go I had problems, 2nd day I had an engine light, took it back, he was snooping around under the hood, after 20 min, mechanic said "engine is trying to adjust" so he reset the engine light.

2 days later got another engine light, again, 20 min under the hood, and he thistime heread the code and said that the oxygen sensor is slow (i think he said the code was P0133) so hereset it.He said he tested to make sure the oxygen sensor is working good, he said he did a lean test and rich test. He said he pulled one of the spark plugs out to test one condition, and then he did something else (I forget,I think fuel rail?) to test a lean condition. [:'(]

Again 2 days later got the engine light. This time he said this is a "real" problem and I need to replace the front sensor, he installed aNGK brand sensor.

Noticed the car was drinking way more gas than normal, reported this to mechanic, he said since I got the new exhaust car will drink more gas, lost about 90miles/150km per tank of gas. But car was running fine with no other problems so I figured that was all.

In April, I start to hear a rattling sound under the engine, could not go to mechanic, he was gone on vacation. Took it to a buddy of mine, jacked the car up and the rattling sound was coming from the high-flow cat. My friend said the honey comb was lose, which mean the cat had worn out. He told me that if a car is running rich, a brand new cat can be spoiled in 3 months time. By the way, no engine light had come on at this time. Did not know what to do so I left the problem, waiting on the mechanic. About 1 week after that I get an engine light, got my buddy to check the code, P0133, oxygen sensor slow. My buddy, replaced it again with another brand new NGK.

Finally mechanic came back in June, took it back, told him what had happened and he refused to look at it stating that I had done something to the car for this to happening. Had no choice but to leave.

Tired of the rattling sound which is getting worse day by day and the really crappy fuel economy, In September, got frustrated with everything, so decided to bring everything back to stock. My buddy help with this, we lifted the car, removed the performace headers, cat, muffler. Replaced with brand new OEM header & cat, 2 new NGK oxygen sensor and the rest we got from scrap (down pipe, middle piple and muffler).

Right away noticed a slighthly better fuel mileage (but not nearly as good as before). No more check engine lights!

In December, got the dreaded check engine light again! This time it was P0420 (catalytic converter operating under efficiency threshhold). Which meant the car was still running rich.

That is my story, my su****ion is on my original mechanic, I believe he did something to my car or maybe forgot to do something which he was fiddling around to fix my original problem.

I took the car to Honda and wasted 1 hours ($90) in troubleshooting, but the guy told me I need new oxygen sensors. I dont believe that is the case because I have gone through 4 oxygen sensors in 1 year. So that is something else which is causing the car to deliver more fuel that required.

Any ideas would be much appreciated.

For anyone that can help me out with this, I would be willing to offer a small reward for your time and effort (please keep in mind - not a rich guy )

By the way, if anyone wants pics of my performanceparts when they were installed, I have it fully detailed so I can post them.

take care,

 

You need new oxygen sensors. More specifically, when the "mechanic" extended the wires he screwed up how well the ECU can read the sensor. The wires are not just wires, they have special attributes and if you extend them with your normal old wire you're going to screw it all up.

In other words, yeah, you'll need new oxygen sensors. Just don't extend them unless you're using wire from another O2 sensor.

 

hey,

thanks for the reply.

actually, when I removed all the performance part, I had removed the wiring that the mechanic had put in there. what he had done was bought extensions (clips and wiring pre-made), then he just clipped it in the oxygen sesnsor. when I removed evertyhing, I removed his extension so its back to stock (none of the factory stuff was cut if that is what you were asking)

can you think of anything else? maybe the mechanic forgot to plug something back in when he was doing the checking..

thanks,