Hi, a friend of mine's 2001 7th Gen Civic just failed the MOT test, due to emissions.

On the test there was only one high reading. Used Cataclean, installed new air filter, & performed an oil change.

On the retest, the reading that had previously failed, was now within limits, but other readings, which had previously passed easily, were now WELL over the limits.

Between test, & retest, the car went over a speed hump too fast, & the underside of the car grounded for a second.

As I was changing the oil, I noticed that there was a bit of damage to the rectangular plastic connector(?) on the downstream lambda sensor.
The connector wasn't smashed, but the plastic block had obviously had some contact with the ground, & was slightly misshapen.

Is this likely to have affected the sensor readings, due to internal damage to the sensor connector block? There were MASSIVE differences in the readings between test, & retest, so something drastic has occurred.

If I found a Civic in the scrapyard, would replacing the wiring around both sides of the connector, solve these faults in the emissions readings?

Maybe someone on here has experienced these problems before, & fingers crossed that I can get some suggestions on curing this problem.

Cheers!

 

Downstream sensor doesn't affect the engine mixture at all, it is only there to analyze the output of the cat to see if it is doing anything, and throw a P0420 if it fails. So if you have no CEL on, the sensor is still OK.

Which pollutants are failing?

 

Hi, thanks for your reply.
I don't have the fail cert here, but I remember that O2 was high.
From memory, there were 3 high readings.
All were within permitted levels before retest.
The exhaust gasses smelled quite rich, so probably overfuelling.

I just texted my friend, & asked for a pic of the emissions fail info.
I should have it soon. I'll post the info as soon as I get it. Cheers!

 

Hi, just got the readings.

First test:

FAST IDLE
CO level - 0.42 (fail)
HC level - 119ppm (pass)
Lambda - 0.98 (pass)

SECOND FAST IDLE:
CO level - 0.43 (fail)
HC level - 118ppm (pass)
Lambda - 0.99 (pass)

Retest:

FAST IDLE
CO level - 0.09 (pass)
HC level - 32ppm (pass)
Lambda - 1.09 (fail)

SECOND FAST IDLE:
CO level - 2.29 (fail)
HC level - 233ppm (fail)
Lambda - 0.94 (fail)

Lambda passed on MOT, but failed on retest, & the other readings have gone crazy!

Does this point to anything in particular?

Cheers. P.