Emissions Issues- Help

HI, I need your help.

My 2004 TF has failed its MOT on emissions and I don't know how to get it to pass. I've tried a few things, and I'm rapidly getting to the point its just not worth spending more money on.

The emissions readings gave the following:

CO: 0.000%
HC: 1.4 ppm
Lambda: 1.345

I first tried an Italian tuneup and drive it hard for 30 mins and dropped it off straight into the MOT bay for retest. However, no luck.

The failure is on the Lambda. A scan with Pscan showed an electrical issue with the post cat oxygen sensor. This was replaced by a garage and the code is now gone, but the lambda hasn't come down.

The garage can't find "any obvious issues", and only recommend "sending the car to an ECU specialist".

Any thoughts?

From your errors and emmision test result I am seeing that you have problems with pre-cat lambda sensor. I would change pre-cat lambda sensor for new one and retest. From what you described pre-cat lambda sensor was not chaged.

Correct. Only the post cat, as that was the only one returning an error. On my way to pick it up now and find out the damage to my wallet, apparently they had a right time trying to get the old one out. I’m getting pretty worried that this is costing more and more.

Not sure if you know but the pre and post cat lambdas are the same part so if they have just replaced the post cat lambda and it didnt make any difference you can reuse the one they took out in place of the pre cat lambda

That’s good to know. According to the garage there has been some amateur electrician work going on with the old one. So. It sure how much of a good idea reusing that one is. Maybe a used one from mgfntfbitz is the best way to go…

Darren at 'Bitz would be a great source. I ended up with a spare (tested) lambda when I bought a front pipe from him a while ago so let me know if you draw a blank and you can always borrow mine until Darren gets another one in.

The “amateur electrical work”, a pound to a penny will be the grafting on of the old connector on to a general purpose sensor.
I did some work quite recently where I amassed sensors from several types & makes of car, the characteristics are so close as to make you ask why such a price disparity.
I didn’t assess the dynamic characteristics of each by screwing them into the car, in turn & run it. Those tested gave similar results.
At the end of the day you’re looking for an MOT pass, the test is academic.
M

That sounds very likely. I didn’t personally see it, but from the description of what they removed it sounds like the error code could have just been the bad wiring job more than the sensor. It has a new Bosch one now though.

Is there anything I can look at in the live data from PScan to establish the health of the not-yet-replaced pre-cat sensor?

Considering Bosch we’re the “patentees” of this type of sensor you can be sure it will be within tolerance. Unless it’s a Bocsh, who are a Chinese maker of poor quality rip-off stuff. That’s an untruth but could easily be correct.
Change the other sensor & run the system stinking hot a couple of times & you’ll be in with a very good chance.
Unless the cat’ has croaked.
M

The Lambda reading in the MOT is the ratio of HC against CO.

The pre cat lambda probe on the car is reading this ratio and the ECU is using that info to adjust the fuelling.
The post cat lambda probe is merely confirming to the ECU that the rest of the system is working, it plays no part in adjusting the fuelling.

Andy, have you got a pass now?

Car spent a while with a diagnostics place - their analysis was that "The car is not holding a stable RPM at test speed and is throwing off the test". They were able to get it though the test, but suggested it may be a deeper ECU calibration issue. Not sure sue what I should read into that, but at least I have the car back now.

ECU calibration issue?????? unless your ECU has been remapped and badly at that.....then I suspect they don't have a clue what they're talking about perhaps they work to the principle of:
If you have no idea of what you're doing, talk a load of shit, with plenty of technobabble, gravitas, authority and a straight face, in the hope you bamboozle the audience.
Politicians TV presenters and senior management do it all the time!