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[amba]

Car has just failed mot due to exhaust emissions lamba reading at fast idle.
Question is ...early december had nearside catalytic converter and lamba sensor replaced as internal "brick" had become loose and was causing major rattling.....now I now lightening tends not to strick twice but would this now point to needing to replace the other cat and lamba to get the emissions within limit,as I can,t think of any other reason ?

[rustym95]

The cat should be fine may be the lamba sensor check that it has good connection to its plug, and the wires are in good nick, may of hit somthing and its hit it. also back box  and mid box can affect the emmisions.

[TheBoy]

Post up the emissions readings

[amba]

Fast idle test:              FAIL
2750-3250------------rpm
CO2   <0.30xvol
0.79%vol                   FAIL
<200 rpm vol
110ppm vol               PASS
0.970-1.030
1.056                        FAIL

Did notice that the test sheet printt out was for engine X20SE/OHC.......but doubt if that would be grounds for complaint even though mine is a X25XE

[rustym95]

test setting are dif on a 2.5 than on a 2.0. so would ask why it says 2.0,. go and ask.

[TheBoy]

Are you sure the car was fully up to temp (ie, did they measure the oil temp via a dipstick temp sensor?)

[TheBoy]

test setting are dif on a 2.5 than on a 2.0. so would ask why it says 2.0,. go and ask.

Nope...

[Kevin Wood]

test setting are dif on a 2.5 than on a 2.0. so would ask why it says 2.0,. go and ask.

Nope...

Indeed. Settings won't affect the measurements, only (perhaps) the limits, although I doubt it in this case.

If it was fully warmed up it's running a little bit lean so check for air leaks into intake or exhaust that could upset the lambda sensor reading. EGR might also be something to suspect, although usually you'd have a rough idle if it was failing to close fully.

If the tester is amenable it might be worth testing each tail pipe in turn to see if you can take a guess as to which bank is causing the problem.

If they've got a code reader that can do live data it might be useful to look at the fuel trims.

Kevin

[amba]

Idle is very smooth and car has been generally running very well for some time(but don,t want to tempt fate !!)
My conlusion was that as I had changed 1 lambda sensor a while ago the other side might now be on its way out,although this was replaced with the nearside cat as the inside had become loose.

[guncharmer]

Last year i had a jaguar XJ8 3.2 sport(V8),it failed on emissions quite badly. a local jag specialist quoted me £600 for secondhand cats!  I took both lambda sensors out(they were on the manifold downpipes and in the engine bay). totally sooted up and apparently a downside to this is it makes the fuel run rich and only exacerbates the problem.Cleaned them with lashings of brake cleaner and blasting with an air gun and prodded all the holes clean on the outer cover they had. straight back for mot retest and passed the emissions with flying colours.Just thought i would mention it. a few skinned knuckles but no cost.

[amba]

Good thought but where omega lambda sensors are positioned means they get the exremes of hot/cold so tend to get totally stuck and brake-off when trying to remove.
Might give the old lambda sensor a good dose of plusgas over next day or so ands see if it does remove...worst case is it snaps and end up with a new cat and lambda as seems to be the conclusion,but might get away with just the sensor.