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Discussion Starter · #1 ·
I have just dug out the MOT for Kat's car as its tax disk time and I notce that on the paper work for the emissions it has the following:

Fast Idle
Engine sped=2759 rpm
CO=0.13 % vol
HC= 15ppm vol
Lambda= 1.024

Natural Idle
Engine Speed=883 rpm
Co=0.48% vol

These are all passes but the Lambda is almost at the upper limit (1.03) and the natural idle CO is high (max is 0.5).

So what do I need to look at to get these figures down? (or are they OK) Car is a 2.3FPT Auto which does about 32MPG on motorway driving.

Steve
 

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I had similar results for my Aero last year, but the lambda was so high it failed. Injector cleaner ("dump-it-in-the-tank" stuff) brought the CO down to almost nothing, but did nothing for the lambda. The tester managed to get it to just touch the limit briefly on the re-test.

I finally tracked the problem down to the intake air temperature sensor (it's a Trionic car) which was only just out of spec. and fooling Trionic into underestimating the air mass, and hence the amount of fuel to inject. it wasn't far enough out to trip the "Check Engine" light.

A new sensor (about £20 from the dealer) cured it and the car went like it hadn't done for ages (after adapting for about five miles).

If your car isn't Trionic (i.e. if it has an air mass meter), then this doesn't apply. I know at least one other person that had high lambda (within limits, though) on a 2.3T auto, and the same fix worked for him too.
 

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Originally posted by StephenA:
[qb]Its a K reg if that makes it easier.[/qb][/b]
Nope, it doesn't make it any easier, as K-reg is around the time Trionic came in. If there is just a plain plastic tube between the air filter and the turbo, without the Air Mass Meter (it will have a wiring harness) making up part of the pipe, then it is Trionic. Trionic cars don't have an AMM.
 

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Discussion Starter · #5 ·
Bill,

Between the airfiler and the turbo is a box with Bosch on it and a cable running off.

So I think I can assume its not a trionic - so are there any suggestions on how to get CO and Lambda down on these?

Steve
 

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The CO should still respond to injector cleaner. Dirty injectors give a poor spray pattern that matters most at idle (at wide open throttle, there is so much fuel the engine doesn't care how it comes, just as long as it does, and the high airflow mixes things up quite well anyway). I used quite an expensive one from Halfords at about £12 or £13 for a single treatment. I was desperate and didn't feel it worth trying the cheaper ones in case they didn't work.

As for the lambda, it could be the lambda probe itself. I believe that if the element is sooted up a bit, it will not see as much of the oxygen in the exhaust gas, so the system will only be satisfied that the mixture is correct when it is actually a bit weak. I have heard that blasting the element with a blowlamp can burn off deposits and restore proper functioning. Alternatively, you could buy a new one, but they're not cheap from Saab. I have had good results with a universal one, but you need to connect this into the existing wiring harness, as it doesn't come with a connector for any particular car.

I'm told an exhaust leak can give a high lambda reading at the tailpipe, even if the mixture is correct.
 

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Lambda sensors are quite delicate and easily damaged - although can be cleaned with care. The cable connecting the lamda sensor is also sensative to the performance of the sensor and must be handle with care too.

Euro Car parts sell one for Saab 9000's (should connect direct - as far as I know) for around £65, which is a fraction of the main dealer price!
 

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I had a lambda sensor problem a while back- tried a couple of "indy" units (Behru as I recall) to no avail. A bit of digging around unearthed some anecdotal evidence that some Saabs are fussy about having the lambda sensor exactly with spec or they will show a fault. So I gave up and paid the difference for an OEM (Bosch I think). From memory I think it was about £45 for the Behru and £80 for the Bosch.

Very often the non-OEM units don't have the connectors but come with splicing terminals.
 
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