Elise (Rover K-series) failing emissions test

Elise (Rover K-series) failing emissions test

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Ganglandboss

Original Poster:

8,294 posts

202 months

Tuesday 7th July 2015
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I have a '99 S1 Elise. It is the 118 BHP model with the 1800 Rover K-series. It is standard other than a Hurricane induction system, Magnex exhaust, Eliseparts high flow sports cat, Eliseparts flexi section and some non engine related mods.

It failed it's MOT a couple of years back on emissions. I discovered the centre section was blowing, so I replaced it. I was advised to check the engine mounts and exhaust mounts, as they are probably at the end of their life. I found they were, so I replaced them.

When I was ready for an MOT, I took it to a garage where a mate of a mate worked. They told me it had failed because they couldn't complete the emissions test, as it had thrown the contents of the coolant system out.

I got it home, but due to other commitments, I have had no time to sort it. I did check for leaks though, and I found diddly squat wrong with it. It developed a really bad exhaust blow shortly afterwards.

My suspicion was that it was blowing from the flange between the manifold and enter pipe, but I was unable to get it in the air to check.

Now I have some spare time, I managed to get it on ramps and checked. The flange was fine, but I did discover a blanking plug in the centre section was missing. Eliseparts told me there was an error when the centre sections were manufactured. Apparently the Lambda sensor is on the centre section on the Toyota engined cars, and their manufacturer misinterpreted a drawing. They sorted this by fitting a plug. I have no idea how it came out; I can only suspect it vibrated out.

I decided it was also worth checking the lambda sensor and it fell apart in my hand. One new sensor and a blanking plug later and she's purring.

I took it for an MOT today and it has failed in emissions. It is okay on natural idle, but well over on fast idle.



Since changing the Lambda sensor, it has only run at idle and had a short run to the garage. They said an Italian tune up may be the answer. I will give this a try, but I was wondering if there is anything else I could check. Any advise would be appreciated. smile

Pumaracing

2,089 posts

206 months

Tuesday 7th July 2015
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Both the CO readings and lambda readings are well rich and both match each other correctly on my reference chart. This means it's not just a matter of the cat failing to clean up the emissions properly - too much fuel is actually being injected in the first place which means the closed loop system is not working properly.

It may be that if it's been running with an exhaust leak for a while then the short and long term fuel trims are well out and it'll take some time for the system to self correct. Longer than the brief run to the garage after you fixed things. I'd give it a good run if you can legally take it on the road and if not then just start the engine and let it operate at various rpms between idle and about 3000 for as long as possible without it overheating.

For reference these are the approximate CO and lambda values that match each other if there are no air leaks present.

CO %...Lambda
5.0 %...0.87
4.0 %...0.89
3.0 %...0.91
2.0 %...0.94
1.0 %...0.97
0 %.....0.99

Yours matches nicely at mid way between 1 % and 2 % CO. When the two don't match it means other problems are present but we don't need to worry about those here.

HC (unburned fuel) is also very high so I'd check the plugs and leads.

Edited by Pumaracing on Tuesday 7th July 21:04

Huff

3,141 posts

190 months

Tuesday 7th July 2015
quotequote all
Don't most ECUs reset long-term trims (because they are volatile memory) if you just disconnect power to the ECU for long enough, say >10-15mins? Perhaps worth a go if you can't drive it on road /under part range load as suggested.

Pumaracing

2,089 posts

206 months

Tuesday 7th July 2015
quotequote all
For those with a mathematical bent I have an equation I use to predict the MOT lambda value from the recorded CO reading if there are no air leaks.

(14.5-(CO% x 0.37))/ 14.6

For the first test, CO 1.681% this predicts. (14.5-0.622)/14.6 = 0.951 (tested 0.952). Spot on.

For the second test, CO 1.518% this predicts. (14.5-0.5617)/14.6 = 0.955 (tested 0.955). Spot on.

Hurrah for maths smile

stevieturbo

17,229 posts

246 months

Tuesday 7th July 2015
quotequote all
You have fitted the lambda sensor in the correct location then ? ie before the cat ?

Was it a cheap generic sensor, or a branded unit ?

Did anyone actually test the sensor output after fitting to see if the system is working correctly ?

You mention various modifications. Has the engine ever passed an emissions test with these modifications ?

Ganglandboss

Original Poster:

8,294 posts

202 months

Tuesday 7th July 2015
quotequote all
The lambda sensor is in the same place as the original (the port on the exhaust manifold. It was from www.eliseparts.co.uk - I have bought many parts from them in the past and never had a problem, so I doubt it is generic crap. I have not tested the output. It has passed MOTs with all the mods.

Pumaracing

2,089 posts

206 months

Tuesday 7th July 2015
quotequote all
Huff said:
Don't most ECUs reset long-term trims (because they are volatile memory) if you just disconnect power to the ECU for long enough, say >10-15mins? Perhaps worth a go if you can't drive it on road /under part range load as suggested.
I believe some ecus do reset LTFT with battery disconnected and some don't. I have no idea about this particular model but it's a good idea and can't hurt.

Theoretically the STFT should adapt to the new blanking plug and the previous LTFT fairly quickly but if the LTFT values are abnormally high it's best to ditch them.

Ganglandboss

Original Poster:

8,294 posts

202 months

Tuesday 7th July 2015
quotequote all
Pumaracing said:
HC (unburned fuel) is also very high so I'd check the plugs and leads.[/footnote]
Could that affect the CO reading as well?

Pumaracing

2,089 posts

206 months

Tuesday 7th July 2015
quotequote all
It's more the other way round. As fuel mixtures get rich then not all of it burns so HC readings go up. It may be that when the A/F value is corrected the HC will also go down but I'd do a compression test if you can and a full check of the ignition system.

You may have a bad cylinder which is raising the HC readings.

mighty kitten

431 posts

132 months

Wednesday 8th July 2015
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Couple of things , if it's failed the full emissions test they should have at least taken the oil temp to prove the engine was fully warm and as the co is well within the idle limits I would pop back and pay a few quid for 5 mins on the gas tester with the engine properly warmed up and sit it a 3000 rpm and see if the levels start dropping . I've seen this countless times where it would fail if I let the time run out for the basic emissions test but raise the rpm out of the upper limit when your measuring rpm which you should do on a full cat test as well as measure oil temp the levels drop once the cat is lit . 8 out of ten times this is all that's needed if co is around 1.5 % and lambda slightly low .

mighty kitten

431 posts

132 months

Wednesday 8th July 2015
quotequote all
Couple of things , if it's failed the full emissions test they should have at least taken the oil temp to prove the engine was fully warm and as the co is well within the idle limits I would pop back and pay a few quid for 5 mins on the gas tester with the engine properly warmed up and sit it a 3000 rpm and see if the levels start dropping . I've seen this countless times where it would fail if I let the time run out for the basic emissions test but raise the rpm out of the upper limit when your measuring rpm which you should do on a full cat test as well as measure oil temp the levels drop once the cat is lit . 8 out of ten times this is all that's needed if co is around 1.5 % and lambda slightly low .

Ganglandboss

Original Poster:

8,294 posts

202 months

Wednesday 8th July 2015
quotequote all
Thanks to everybody for the advice. I have bought new plugs, dizzy cap and rotor arm and had a look at the ignition. The plugs are very lightly carbon-fouled. There are a few deposits on the points and the HT lead plugs at that end were a bit crudded up. They were rust deposits at the spark plug connectors and a bit of corrosion on plug 3 - this is common on Elises as rainwater falls through the engine cover vents and collects on the top of the engine.

I noticed another problem - I cannot get plug 2 out. I could feel the socket was not engaging, so I shone a torch down the hole. There is a bit of black plastic at the side that is stopping the socket engaging. I've stopped for the night, but I'll get some long forceps tomorrow to remove it. The plastic in question has broken off the HT lead. I don't think it affecting the integrity - it seems to be there to align it with the port rather than as insulation. I'll order some new leads though, as the water ingress may have taken its toll. The Eliseparts ones are supposed to have better protection against this problem.

The retest is free, so I'll finish this and run it back one afternoon so I can let her rip when there is no traffic and get it tested while I know the engine is hot.

ETA: I've just had a closer look at lead #2 - it is pretty crappy at the connection.

Edited by Ganglandboss on Wednesday 8th July 22:06

stevieturbo

17,229 posts

246 months

Wednesday 8th July 2015
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Your car has points ?



Wow.

supermono

7,368 posts

247 months

Monday 13th July 2015
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Spark plug points from context, I read. Could be wrong smile

Ganglandboss

Original Poster:

8,294 posts

202 months

Thursday 16th July 2015
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I'm at the garage now - it's passed...just!

Pumaracing

2,089 posts

206 months

Thursday 16th July 2015
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I'll be interested to see the new emissions results.

Ganglandboss

Original Poster:

8,294 posts

202 months

Thursday 16th July 2015
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I'll post again when I'm at a PC, but CO is bang on the limit. HC has come down significantly.

Ganglandboss

Original Poster:

8,294 posts

202 months

Thursday 16th July 2015
quotequote all


As I said - right on the limit!

I took her back to the garage this morning. I made sure I did so after rush hour so I could give it a bit of a kicking again, and get it straight on the tester whilst still hot. It also needed a headlight adjusting, so they did both at the same time. I was sat in reception, watching through the window. I was getting worried, and the receptionist commented that it had been on a long time. She went into the garage to ask, and came back saying 'It's failing on the cat one'.

After a while, I thought I heard the word's 'It's passed'. The receptionist's ears pricked up too, and she went back in to ask. A moment later, a smiling mechanic came in holding up the key. He said he thinks the cat is on its way out, and said the fact it has been stood won't have helped.

Obviously I'm chuffed to have an MOT, and the sun is shining, and it is now taxed! However, I still need that number to come down. I'll probably drop it in again in a few weeks and see if it has dropped any more. I'm also thinking it may be worth running it to a Lotus dealer and getting them to put the diagnostic on it.

One thing that did seem iffy was the rev counter was erratic after I changed the leads. Engine RPM is measured from the crank position sensor, so nothing I have done should have affected it, but it is still a concern. The Lotus service notes say the engine will default to a rich mix if a sensor fails. The rev counter did not work at all this morning, but came back to life after a few minutes. I asked if they had seen anything odd on the first test, but they said they didn't recall anything.

Thanks a lot to everybody who offered advice! beer

Pumaracing

2,089 posts

206 months

Thursday 16th July 2015
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Ok, let's analyse the readings mathematically again. CO value is 0.30%. Predicted lambda if the A/F mixture is genuinely too rich is 14.5-(0.30x0.37)/14.6 = 0.985

Actual lambda is almost 1.0, i.e. perfect so the conclusion is the A/F is now correct and the new oxygen sensor and closed loop system are working correctly but the cat is not cleaning things up fully. You'll probably need a better one before the next test.

HC is now much better with the new plugs and leads but still indicates a somewhat less than perfect combustion. Probably just bore and valve seat wear but the head gaskets are weak on these and a compression test would still be a good idea.

Edited by Pumaracing on Thursday 16th July 15:06

Pumaracing

2,089 posts

206 months

Thursday 16th July 2015
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Rather than type it all out again I refer to my post from a couple of years ago explaining the Brettschneider equation for calculated lambda values and its relevance to MOT emissions failure analysis.

http://www.pistonheads.com/gassing/topic.asp?t=121...