Tuning Supersprint Manifold & Failed MOT

[sid23456]

Hey,

Have a Punto Mk2 Sporting with a supersprint manifold and 200cpi sports cat.

Only have 1 lambda sensor on my car pre-cat. (Bought a cheap lambda sensor off ebay last year).

Failed my MOT with reading

Lambda= 1.11 and 1.09 (Limit= 0.97-1.03)

Passed on all other emmision readings.

Now I'm wondering whether it has failed because of the cheap lambda sensor, the sports cat, or whether due to only having 1 pre-cat lamda sensor.

Any ideas? Don't want to start spending unnecessarily?

 

[rallycinq]

When was the car last thrashed?

Small leak somewhere?

Cheers

SPD

 

[Kalev]

Add 10% E85 and it should pass hopefully

 

[sid23456]

Gave the car a good run just before the MOT. Got the old original lambda sensor so was going to fit that before the retest.

Been looking at E85 stations, and there's nothing near me. Anything else that might work?

 

[dave]

if you have no hole for 2nd lambda it should be plugged in an wrapped in foil.

in this weather though it can still be to cold to get proper reading, had mine done back in october an still had to rev it high for a few minuets, then bring it back to idle to get a pass.

even though fan was cutting in an out loads like it should

 

[fingers99]

New plugs help. My friendly local MOT place lets the fan cycle at least twice before doing the emissions.

 

[sid23456]

if you have no hole for 2nd lambda it should be plugged in an wrapped in foil.

what do you mean by this? When I changed the original manifold, there was only 1 lambda plugged in. IIRC there are 2 lambda boss/holes in the supersprint manifold. The top one was open (plugged the lambda) the bottom was already sealed.

 

[dave]

mk2 sportings should have 2 one post cat, i pre cat.

if you dont weld a hole for the post cat one after your sports cat, then wrap it in foil

 

[Liquidh2o]

mk2 sportings should have 2 one post cat, i pre cat.

if you dont weld a hole for the post cat one after your sports cat, then wrap it in foil

I have a 2000 sporting mk2 and it only has 1 pre-cat lambda sensor. I think somewhere along the line they added the post0cat sensor for the euro3 emission tests or whatever they are called.

 

[dave]

hmm maybe a proper oem sensor instead of cheap ebay one will fix it then

 

[Liquidh2o]

yes most likely, it will be the ebay sensor. Did you buy one of the lambda sensors with the pigtail wires that you needed to connect to your own original plug? And if so, did you perhaps solder the wires together? This alters the wires resistance and will influence the readings of the sensor.

 

[Punto_Pete]

i've got a 200 cell cat on the hgt and it doesn't quite get hot enough, unless it really thrashed just before taking the reading. it's quite common even on standard cars. i'll wrap the manifold eventually.

 

[sid23456]

yes most likely, it will be the ebay sensor. Did you buy one of the lambda sensors with the pigtail wires that you needed to connect to your own original plug? And if so, did you perhaps solder the wires together? This alters the wires resistance and will influence the readings of the sensor.

Think I did solder the wires. Screw it, I'll juts put the old one back on or just buy a new original, and give the car a proper thrashing before I retest.

Thanks

 

[sid23456]

Just to update this has been a real pain.

Bought an original lambda sensor, got it fitted and emmisions were fine (within MOT limits).

Took it for my MOT retest 4 days later...emmisions were worse than before! Carbon monoxide readings were double the limit and lamda reading still high.

MOT tester said the readings might be off, as he was struggling to keep the fast idle revs steady...possibly a running issue?

Anyway, just swapped over the original manifold and cat, plus still had the sports cat on, and emissions were really good again.

Car's are a mystery!

 

[arc]

Lambda is a measure of air:fuel, on an MOT the lambda readout has NOTHING to do with your cars own lambda sensor.

A high value just means there is too much o2 in the exhaust, either running lean or you have an leak on the exhaust. You've wasted your money buying a new sensor.

 

[dave]

MOT tester said the readings might be off, as he was struggling to keep the fast idle revs steady...possibly a running issue?

tell him to just leave it on normal idle then, the machine wont know