mot problem

[martyn roberts]

Hi, have just had my elan mot, and has (only) failed on emissions the guideline should be around 3.5 % co but mine is reading 7.4% - 8% can anyone point me in the direction for reducing this figure to enable a pass. the car has alwas run on the rich side since purchasing it. am i right in thinking it maybe the CTS. Or am I barking up the wrong tree.
Don't have elan scan etc.

[chris.t]

there is a eprom chip (cost about £15) it went on mine and causes the emissions to go ott. Someone will be along to give you the full description.

[Enright]

So it's an SE, right? They all run a bit rich as a safety feature.
Running lean can be catastrophic, especially for turbocharged engines.

Your diagnosis might not be too far out, or it could be the early signs of CAS failure.
But I'd get the timing set right and plugs gapped properly before I started wasting any money on potentially un-necessary sensors.
Also do a paperclip test to see if any fault codes are stored - could be a good pointer, and again a free DIY job.
Then maybe it would be worth seeing if there's anyone not too far away who has Elanscan and could do a log for you.
I bought a Gunsons CO tester off eBay - they're pretty cheap and while not hugely accurate, they can at least show you the effect that you're having on emissions while fiddling, which could save you the cost of another re-test.

Another way of absolutely whacking the emissions on the head is to buy a 3 wire O2 sensor from Rockauto.com, and an S2 chip from Alan (ESM). Your emissions should then come down to about 1/10th of what they currently are!

[John_W]

Martyn,
Is it an SE or S2?

If an SE, check if it still has the original chip or if it's been replaced with the "low emissions" version Lotus put out to deal with new emissions tests. If you don't have Elanscan, you should be able to tell by looking at the ECU. If the seal is still intact, you need to change the chip; if it's been sliced, or has something written on it in felt-tip pen, then you probably have the new (9930) chip already and you problem is elsewhere. In that case do as Neil suggests. Remember that the CO pot (attached to the ECU) adjusts emissions at idle.

If it's an S2, you'll have to ask somebody else.

John

[ailwyn]

Then maybe it would be worth seeing if there's anyone not too far away who has Elanscan and could do a log for you.

Martyn,

I can meet up with you and hook ES up to your car.

As has been suggested, try turning the co-pot down to it's minimum, see if that will get you through the test.

Ailwyn

[Enright]

Ailwyn, I'd recommend caution before messing about with the CO pot - IIRC it doesn't have a stop, so you can turn it til the cows come home and completely lose your starting point. But the adjustment is pretty fine on it, and half a turn either way can make a massive difference.
So without a gas analyser up your car's jacksy, you can really bugger up the emissions with very little effort!

[ailwyn]

But the adjustment is pretty fine on it, and half a turn either way can make a massive difference.
So without a gas analyser up your car's jacksy, you can really bugger up the emissions with very little effort!

Never listen to an S2 owner

I still think that to co-pot would be the best approach initially.

I assume a gas analyser is a standard part of garage kit?

Ailwyn

[Enright]

I still think that to co-pot would be the best approach initially.

It's certainly a good place to look, but only after verifying that timing and plug gaps are correct.
Those always ought to be done first, or you're just tweaking the adjustables to compensate for incorrect base settings.

I assume a gas analyser is a standard part of garage kit?

Ah, I see where you're coming from there, and yes I agree it should be.
Perhaps I didn't make it too clear, but I was approaching it from the standpoint of the home tinkerer. The guy who is doing as much as possible to ensure that he takes his car to the garage JUST for them to give him the MOT certificate.
And that's simply because as soon as you go through the door of those places, £'s start racking up on the bill, and I'm very keen to give as few of mine away to them as possible!

[martyn roberts]

Crikey, I thould everyone would come back with one unanimous fix,
Just typical, nice weather at last and can't use the car,
right, I have changed the CTS this AM, I had a new one spare anyway, the Co readings have not changed at all.
The garage where car is, changed the belts etc for me so there should be no problem there.
I shall try and find the CO pot and adjust Monday at garage does it adjust easily
My elan is 1991 SE pre cat converter model; so no O2 sensor
Whats a eprom chip, is it the same as a S2 chip
Whats a CAS failure it sounds bad to me
Can't check for chip types till monday after work, cars locked away at MOT garage till then.
Where could I get a low emission chip from, it sounds like a good idea to get one anyway.
I am reluctant to do anything electrical in case I make things worse
Maybe Ailwyn you could pm me to arrange a scan and show me the secrets of a paper clip test I would'nt know a fault code if I saw
one at moment

[John_W]

Martyn,
It may not sound like it, but we are all saying basically the same things:
first check your adjustments are OK (timing, plug gaps, CO pot), and only then start suspecting sensors to have failed (eg CTS, CAS), in which case ElanScan will confirm what readings they are putting out and help you find if one is faulty.

Have a search through the forum for some others who have had MOT emissions problems. Here are a few to start with:
CO Pot adjustment.
CO pot adjustment instructions from the manual.
Typical emissions values.
Paul_W with a similar emissions problem.

Good luck,
John

[GeoffSmith]

Information on the 'low emission' PROM is on ESM's website. If you can't trim out the emissions to meet the MOT levels, then you may need an upgrade.

I've always found my local MOT garage helpful, and if I told them what to do with the CO pot to reduce the levels, they would do so just before testing it (to reduce time and cost).

I don't know what the availability of Lotus upgrade PROM is, but if you haven't had the upgrade then I have some blanks which I can program up if you have a problem.

Geoff