Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[greeno]

My 2.5 V6 failed mot on Lambda emissions. They are high. Garage said have engine code check done to see if this can help track down the fault.
Engine management light isn't on.
Is the code check worth doing if engine management light not on? Thanks

[Jimbob]

Hello & Welcome.

Yes in a word...most faults dont actually cause the light to come on, including some that can and do cause breakdowns.

so do the paperclip test - see my signature on code reading and post up the results and we will see how we can help.

other things are put some top quality fuel in, and or injector / fuel system cleaner /  cataclean, and drive like a maniac to burn out any rubbish.

But start with a code read, and we can see if there is an obvious issue.
do you have your mot emissions readout, may also help to see if your way off, or borderline.

[henryd]

My 2.5 V6 failed mot on Lambda emissions. They are high. Garage said have engine code check done to see if this can help track down the fault.
Engine management light isn't on.
Is the code check worth doing if engine management light not on? Thanks

Bear in mind that a small exhaust leak will also raise the lambda readings,it may be a leak that would not neccesarily fail the test but could mess with the readings

[greeno]

Thanks. Just run the test. No codes showing other than 12 when engine on, with 12 and 31 while engine off.
on first 'short' mot test lambda was just over at 1.032  other readings ok. when did full test first fast idle was a fail on co but pass on lambda, while second fast idle was ok on co but fail on lambda....guy said "something screwed up here"
had new exhaust on recently. Secondary air mass not working i think makes noise on start up.

[Jimbob]

secondary air injection only helps on cold - mot is done hot.

just unplug the SAI pump - under pass side of front bumper, dont bother with it.

least you have no main faults to sort.

so theroetically, you car has passed both parts of the test....

Id be putting some fuel cleaner in - like forte advanced formula gas treatment, some good fuel.
Do some driving, keeping it in the high rev band, then get it retested, must be close on a pass.

[greeno]

sounds promising. Do you know if no fault code means that my lambda sensors are ok?

[bigdods]

on first 'short' mot test lambda was just over at 1.032  other readings ok. when did full test first fast idle was a fail on co but pass on lambda, while second fast idle was ok on co but fail on lambda.

I had something similar on one of my other cars. Second fast idle passing on CO *could* be just that the cats needed to get hot before operating at full efficiency. The Lambda fail could be an air leak on the new exhaust.

Maybe when things get hot enough for the cat to work the exhaust is opening up an expansion leak at a join somewhere ?

My experience on the TVR was a massive fail on CO , with lambda right on the limit from cold. Took it for a spin, came back and kept revs up to keep things toasty , passed CO with flying colours (cat now hot) but lambda went over the edge. Quick look under the bonnet showed a small leak where the manifolds joined the exhaust. 2 minutes with the spanners, leak solved and all passed.

I cant say for sure that this is your problem but I would say its worth going over all the exhaust joints again. My experience with the TVR the leak was after the lambda sensor, so no faults shown on the ECU , just too much air in the system.

[greeno]

Thanks. Have checked for exhaust leaks, given the advice, can't find any. Going to throw in a can of Cataclean, again given the advice, tonight and give it a run. Will take for re-test with fingers cross....everything seems fine apart from the mot 'fail'!

[greeno]

Given it a good blast with Cataclean in. What I have noticed is the idle speed is now about at my long term 'normal' at 750 rpm whereas before to the blast recently it had been running around 1000rpm. I had spotted the 1000rpm was higher than usual but not really thought twice about it. Any thoughts on why idle rpm may have been running high previously?