My 2.0 Cavalier SRI 16V (Ecotec X20XEV) just failed the MOT due to high CO reading. The CO reading was 0.59% in the high-revs test (around 4000rpm I think) compared with the pass limit of 0.3%.
On the other hand the CO drops to around 0.3% at tickover.
The guy tried his best by running fast for several minutes to see if the CAT would warm-up - but no good.....
All other gasses were OK including Lambda at 1.02% - I recently changed the oxygen sensor.
Does anyone recognise this pattern - it's done 74000 miles on the original CAT but of cause you want to be sure before spending big money on this part.
I changed the air filter recently and it seems to be running OK but maybe more thirsty in the last 12 months.
Any suggestions most welcome.
Thanks
Howard
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These readings could indicate a fault with the catalyst or a leak in exhaust system,but really the live data from engine management system would have to be assessed together with a 4 gas engine exhaust analyser for a correct diagnosis
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I agree; without further testing it is very difficult/impossible to say so - but I woudl 'lean' towards the catalsyt being inefficient at higher gasflow speeds.
In other words, it's getting tired, time for a new one.
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groups.msn.com/honestjohn - Pictures say a thousand words.....
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Yes, I should have made a note of all the values displayed on the analyser - all I remember is that all the others were within limits.
Forgot to mention, but I did run it for a few hundred miles with the duff Lambda sensor (management light on)!! It ran OK and fuel consumption was about the same.
I wonder if the CAT might eventually recover if it's just clogged-up with carbon due to the duff Lambda plug?
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Yes, together with it's age, I'd say that was most likely.
A quality metalcat replacement won't be that expensive.
Avoid the cheap ceramic cored cats.
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groups.msn.com/honestjohn - Pictures say a thousand words.....
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Thanks for all your contributions - anyone know where to get the best deal on a DIY CAT???
Howard
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There is a product called Cataclean that's frequently shown on the Satellite shopping channels. It *claims* to lower emissions - however it could be just another "snakeoil" product. www.systemproducts.com
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Fast idle test is 2500 - 3000 rpm. How clean is the oil and the air filter? Are the breathers clean? .59 is only just out of spec but it could be a slow switching O2 sensor. Easily identified by holding your foot rock steady on the accelerator raise the revs to spot on 3000 (put your left foot under the pedal and push the pedal onto your foot) ((not too hard!!)) and watch the tacho. It should remain rock steady if it is ok but if it wavers between 2900 and 3100 rythmically then the O2 sensor is failing. Replace it with a genuine item.
Andrew
Simplicate and add lightness!!
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Dave - Large pinch of salt required.
Snake oil IMO
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groups.msn.com/honestjohn - Pictures say a thousand words.....
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The air filter is new, but it is close to oil-change time.
Thanks for the tip about the O2 sensor test - I'll try that, but it should be OK because I changed it just before Christmas. It's a genuine GM part.
Howard
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