MX5Ireland

CO2 at high idle.... limit is 0.3, mine is at 0.98.. (94 1.8 Eunos, with a cat)

Car is laid up outside doing one short 10 minute drive every couple of weeks.

Italian tune up and dipethane job ? Any recommendations on how to do that.

mine (98 mk2 rs) was high also last year at .8 or around that. Tried the dipethane thing and that didn't work. It turned out that the CAT was shot and I got used one off Robert (autocheck on this forum) and it brought it down to .02 or that. Its due again in May so will be interesting to see readings a year on. I'd say as your reading is so high at .98 your cat may also be fecked. Also check that you don't have an exhaust leak somewhere. Try to get her out for a good hard spin every now and again. The Italian tune up is just basically driving the guts out of it at high revs every now and again with the idea being to burn off carbon build up.

I failed emissions 3 yrs in a row, diptane worked the first time but not after that again, then failed again next yr and got a replacement cat , then failed the next yr again and had to fork out for a new cat. I wouldn't bother with a replacement CAT if you planning on keeping the car unless you sure its pretty new

New aftermarket cats are useless.Scrap value is 1 yes 1euro where as genuine Mazda cats are worth 44euro for scrap.Speaks for itself really....

This dipethane stuff might be feckin up the CATS.....................

Update after retest:

To recap, original failure was on CO at high idle (2850rpm). It was 0.98% (max level allowed 0.30%).

I ran the old fuel in it down by driving it around and then filled the tank most of the way and added a full litre of Dipetane a couple of days ago.

Thereafter I did about 25 minutes of open road driving, third gear, 5000-6000 rpm at about 100kph last night.

I did the same again tonight and the car went into the test still hot within 5-10 minutes of arriving at the test centre.

CO at high idle is recorded on the test at 0.02% now. That being said although it looked like it flew the test, the tester told me it barely passed... he said when he put the foot down it would shoot way above range for a couple of seconds and then drop right down and hold. On average though it went through.

Something must be going on then.. maybe cat ? or maybe some fuel mixture / too rich / basic service type scenario ? I am not sure (I am a mechanical moron as Robert can attest to !).

Nonetheless its a pass.

the diptane need to be completely flushed to get releiable readings, as in empty tank and then fill up again to get rid of all traces of the stuff

Its a pass yes but it still does not resolve why the car was running too rich.

I am using Dipethane for years and leave your fuel near the red mark and add half litre of Dipethene .Ignore whats it says on the bottle.Then basically the fuel mixture the car is running on at time of test is lean so it will pass unless something is knackered ie cat etc.Do not flushout the Dipethane .I have passed dozens of cars this way incl a Clio that failed on high emissions ,treated it as above, done no other work , and it passed perfectly.If you fill up the tank you are thinning the Dipethane too much.........Low fuel for test with high concentrate of Dipethane.

+1 for the Dipetane. I've been using it in petrol and diesel engines and never had an issue with it.

Just failed today. 0.96 and 2.06% co. The manifold gasket is blowing but I didn't have time to change it. the high co is rich running and CAT shagged.
Anyone know of a good aftermarket CAT ? 2 1/2 Inch bore.............................

Hi Sean ,Most aftermarket cats are good for 1 test only and they tell you that in Motor factors.Clean used at is 10 times better.This is obvious from the scrap value above.2.5 in is bigger than say 1.8 vvt?? We have clean genuine Mazda cats I can cut out of the pipes to confirm they are clear internally but dont think they are 2.5in?, more like 2in maybe

Just checked in the shed and thank god I kept the old mk1 cat. Its much bigger in cross section than the mk2 one that's fitted and I know it was good. Why I thought it was a 2.5 inch system I don't know. Anyways, mig welder is out........................................Yeah Robert, the aftermarket ones don't seem to get good reviews at all. You would be better going to a scrappy and getting one from a recent car and weld in that.

Now to get the Manifold off to replace the leaking Gasket.

Good man Sean.

nice one