HGT MOT failure. Lambda!! Pls advice!!

[Sub]

HGT 155 failed MOT this morning. Did all the usual things beforehand, gave it a hard run for 15 miles at high revs, used STP injector cleaner a few days ago into fuel tank (tank half full now). MOT centre tried hard to get it through but no success. Here are the readings.

Fast idle:
CO = 0.00% PASS (max 0.30)
HC = 14ppm PASS (max 200)
LAMBDA = 1.07 FAIL (range 0.97 - 1.03)

Second fast idle:
CO = 0.01% PASS (max 0.30)
HC = 14ppm PASS (max 200)
LAMBDA = 1.06 FAIL (range 0.97 - 1.03)

Reckon it is the Lambda sensor? Are there 2 lambda (o2) sensors in the HGT, one near the engine manifold and other down in the exhaust, if so which is the faulty one?
I had the same failure in last year's MOT, changed lambda sensor and it passed. Its annoying that this has happened again (if that is the problem)

Any ideas chaps? Need to get the MOT thru ASAP so any help will be very much appreciated.

Thanks.

 

[Paul R]

you only have one...

my guess is that you used a cheap copy lambda, only buy genuine lambdas, buy cheap buy twice.

Paul R

2xHLX owner,3xHGT, (then the darkside) 1xCoupe20vt now the proud owner of a Black Coupe20vt LE!

 

[Buzz]

Those look like very good figures. Its very much time to replace that lambda sensor. I've never tried any of the cheap copy ones, but i suspect that if everything else on your car has passed then you should just let the garage supply and fit one. I imagine they'd know which to replace, or be able to test, but i've never had a hgt, so dont know anything about how the dual lambda system works.

If its only 1 job, perhaps just bite the bullet?

Buzz
The champion of the Bravo 1.4
& now ex owner of a Bravo 1.8

 

[Carroll]

My 'Euro.3' 150 20v Marea has two lambda sensors, (as does my Euro.3 2003 Daihatsu) could'nt say about all the earlier ones, but would assume that the early '147' versions did'nt.

My low-mileage Marea managed 0.03% CO, 15 ppm HC and 1.004 lambda on the 'Fast Idle' (@2850 RPM) test.

As my first two results were very similar to yours, I'd say yours probably is a faulty lambda sensor, but how you, (or the garage) can tell which one, I don't know.
I've read that if two lambda sensors are fitted, the computer works-out the difference in values between the two sensors and so adjusts the fuel mixture accordingly, (but that's from Daihatsu's website, not FIAT's)

 

[Mark]

The 155 HGT only has 1 lambda sensor.

Strange that it's failed again, unless, as said above it was a cheapo Ebay type one..

 

[Paul R]

a decent diagnostic machine will tell you which one.

I wouldnt let the garage change it unless they specify or you specify a genuine one.

Paul R

 

[Tom]

Check other things as well, the fact its done the same thing with a new lambda hints at something else at fault.

Had a cheapy lambda on my car for years, no probs at all when it comes to MOTs.

 

[Paul R]

well check your thermostate, that could cause it also...if you have never had one you are probably due one, but doubt it would knock the lambda out. but you would have probably had the injector light on occassionally if thermostate was screwed enough to cause all this.

what temp does it run at?

Paul R

 

[Tom]

More likely an exhaust leak.

 

[Paul R]

thermostate could cause emission fail also.

 

[Ash]

i got money on it being a leak before the manifold or the cat