Lambda Sensor & Fuel Emissions Fail

[Pedro]

Hi all,

Long time no chat I am hoping for some advice... My Lotus Elise S1 failed it's MOT only on fuel emissions and the garage think it's the Lambda sensor, although when i tested with a volt meter there was voltage starting at 0.8 and decreased as i increased the throttle down to about 0.2 volts, which would indicate that the sensor is working...The garage are still saying it is most likely the lambda as the test showed it as high as 7 on the tests....I have agreed to change the lambda since i have never changed it in the 6 years of owning the car...but am worried it may be something else such as the CAT...any advice most welcome?? Thanks guys, appreciated.

Cheers,
Pete

[Shug]

Standard car?

Worth getting the Cat nice and hot as they always were a wee bit borderline on emissions. Likely if it's sat on their lot for an hour, then started up and put straight on the tester, it'll fail. Your testing on the Lambda does seem to indicate function (although I forget the actual voltage figs, if it's changing related to engine output, then it's not just dead)

However, if it's failing by miles, knackered cat is potential, plus a few other things causing overfuelling such as a clogged up air filter, MAP sensor out, or an air leak in the exhaust screwing up readings, etc... Is it running well generally, or a bit lumpy and sooty?

[Pedro]

Hi Shug,

Thanks for the reply...yeah it's a standard Elise S1 and as you say has always been borderline over the years with emissions testing...usually just passing after I rip up and down the country roads to heat up the CAT...so am kinda expecting it to be the CAT or something else I've agreed to have the lambda changed and retest since I've had the car almost 10 years and have never changed it...and if that fails I am guessing it's the CAT....not sure what the MAP sensor is? But it hasn't been serviced for a while so guess could be a filter or similar.

Cheers,
Pete

[Shug]

not sure what the MAP sensor is?

Manifold Air Pressure sensor. One of the more unlikely ones, TBH.

Given the cost of Cats, I'd be tempted to try all the filter/plug service items before springing for that if you don't definitely know it's dead. That said, if you take it off and there's bits of core rattling about inside, it's a reasonably safe bet it's dead

[Pedro]

Passed Emissions test, after new lambda fitted just need some decent weather now to enjoy running about in my wee Lotus

The mechanic looked to have a bit of a job getting to the old lambda though & had to remove the manifold heatshield.... looked to be a home made one out of stainless steel...I've kept it in case it's needed, altho there didn't appear to be any wiring near the pipes...still nagging me a bit as it must've been there for a reason..? Just hope nothing melts lol

Thanks for the tips and advice guys, i hope to try an catch up sometime altho I think the car is a bit long in the tooth now for Knockhill, I'd like to go along sometime

Cheers,
Pete

[Dominic]

AFAIK that heat shield is really to keep heat away from the alternator - which won't like getting frazzled from the manifold heat.

[Shug]

Lucky he got it out without a gas axe at that age

As Dom says - I'd not run long without the heatshield - I did once and had a surprise when the bulkhead soundproofing started smoking in the rear view mirror....