high co readings at MOT test.

[lauriesmb]

Hi Everyone. Ive just joined the corsa forum, and have a problem that i hope someone can help with.
I bought a 1997 corsa 1.4( ecotec engine) gls 5 door manual last week, cheap, for my daughter in law to use to get to work as her little nissan micra just gave up the ghost.
The fella i got the car from, had just taxed it for six months, and had taken it in for a new MOT, but it failed on a couple of silly things( wiper blade and brake light) plus it failed on emissions test. Specifically, the CO levels were failing on fast idle.
He replaced the cat, the lambda sensor and took it back in, and again it failed the emissions on the same thing, so replacing the cat and lambda altered nothing.
Unsurprisingly, he was really cheesed off with this and just decided to get rid of the car and thats where i come in!!
I bought it off him cheap, knowing it had this problem, but was confident that could cure it easily( and more importantly, cheaply!!).
The car runs like a dream, its good on fuel, very nippy and responsive, doesnt falter or hesitate on aceleration, and drives well. No smoke from exhaust etc.
First thing i did was put in a bottle of fuel cleaner, and thrashed it, engine management light came on after 30 minutes fast drive down the motorway, but went off after igntion turned off and on again, and stayed off.
Air filter was renewed, all exhaust was checked for leaks, none found, in fact it has a new cat, downpipe and full exhaust through to backbox.
No leaks in air system found anywhere, but i did find that the manifold bolts were a little loose, so tightened them up.
Took the car over to my friends garage, and he booked it in for MOT and it went in on tuesday(yesterday), and only failed on the damn emissions again!! same readings, co fail on fast idle tests.
We are both baffled! done everything obvious, engine runs sweet and doesnt miss a beat, so now am stumped!! does anyone have any ideas? Its so frustrating because the car is a little cracker, solid, clean and good mechanics, just this daft emissions bull***t.

[johnny]

take the the cam cover off probably full og gunk, it will just be old built up oil, clean as most of it as you can, do an oil change, good long run then with plenty of high revs if the oilhas changed colour atall change it again, no need for a new filter on the second change, you can flush the if wanted AFTER the long run as it shound have clean most of it,

make sure theres fresh spark plugs

and the best tip is make sure the engine goes into the test as hot as possible, this thins the oil and everything out and really does help, ive seen a month old cr fail on emissions when the engine was cold

[lauriesmb]

Hi Jonny, thanks for that, ill give that a go, ive read also that the crankcase breather tubes can get clogged and the egr valve, so ill clean those as well. My mate has got frustrated with my car because its in his garage and his other customers cars are being delayed while he messes about with my car!.
I checked the corsas mot history, and strangely, it has failed its last 5 mot tests on emissions only, so whatever they did each time to get it passed, is a mystery!! but clearly it was done quickly as the mot was passed the day after the fail on each occassion.
Is this a problem with the ecotec engine? apart from this, the car is great!!
thanks again.

[lauriesmb]

Ok, heres the update. I drained all old oil, flushed and cleaned the engine through. checked the crankcase ventilation pipes( surprisingly quite clean), cleaned egr valve, refreshed with new oil, ran the car up the M5 for about 30 miles each way, and drained the oil afterwards. oil was clean. So refilled with fresh oil, new spark plugs, its had a new cat, new lambda sensor, no air leaks and no exhaust leaks anywhere. Car runs sweet, little bit of hesitation on low rev and acceleration, but otherwise drives great. not using much fuel, and everything seems to check out ok! took it for a good long run then into the retest at 2pm today, where it promptly failed again on the same emissions readings! no change. so after everything done, its STILL failing on the CO readings!! too high.
todays C O reading was 0.80% and the limit is =< 0.30% that was first fast idle test.
second fast idle test was C O reading 0.72%

Natural idle test was 0.66% and the limit is =<0.50%

This has been the same figure(s) each time its gone onto the emissions analyser, so no matter what ive changed or done, its still reading similar! everyones baffled!!! any advice would be gratefully received as i feel like driving the car off the cliff!!!

[lauriesmb]

Could the oxygen sensor cause the high emissons in CO readings?

[johnny]

Do you know anyone with opcom or someone with a live data reader

Since all the basics have been covered, it may be a garage job, unless you can get the live data to find out what is/isnt doing its job

[lauriesmb]

Got it booked into a local garage that has all the equipment. Seems that they have had a few corsas in with same problems and they sound quite confident about tackling it and then do the MOT so gonna leave it with them now.
Will update you as to what happens and diagnosis. thanks for your help.