S1 Elise (Rover/111S Hybrid) Running Rich: High CO & Unstable Idle on Emerald ECU

[niclass1headache]

Hi. I am the owner of a Rover-engined Elise S1, and I am having several combustion-related issues. I bought the car 2 years ago. Right from the start, I was surprised by how much carbon soot it produced and how unstable the idle was, to the point of stalling if I wasn't quick enough to give it some gas. The previous owner told me everything was fine, so I assumed it was just a simple fault.

The following year, I took it for its ITV (the Spanish MOT) and saw the emissions test results: CO at idle was 6.06% and CO at fast idle was 3.33%. At that time, the car was fitted with a Hurricane induction kit, the base S1 engine block, but the cylinder head and camshafts from a 111S.

I took it to a garage, where it sat for almost a year. While there, the exhaust manifold was replaced because the original one was rotten (replaced with a Larini Sport Small Bore), the throttle position sensor (TPS) and coolant temperature sensor (CTS) were checked, and a 52mm Trophy throttle body, an Emerald ECU, and a new Lambda sensor were installed.

The car's emissions have now dropped by half, but they are still 5 times higher than the MOT limit. It continues to produce a lot of carbon soot and the idle remains unstable. Right now, the garage is at a loss as to how to proceed.

I am planning to map two separate maps—one for the MOT and a general one—but that would just be a band-aid and wouldn't fix the actual underlying problem. What do you recommend I do? Where should I start? I am also attaching a photo.

[Badger02]

Hi. Is the garage in Spain you are using a Lotus specialist ?

[niclass1headache]

9 minutes ago, Badger02 said:

Hi. Is the garage in Spain you are using a Lotus specialist ?

I'm living in the very west of Spain (Mérida) and the closest Lotus Specialist are pretty far away. Because of that, I took it to an sport car mechanic. 

[Lithopsian]

Get the diagnostic output and it will either tell you why it is over-fuelling, or tell you that it doesn't think it is.  If it doesn't think it is, then that points to an injector or fuel pressure regulator problem.  Or if you're really unlucky, bad inputs that are hard to spot like a vacuum leak or MAP sensor on the fritz.

[niclass1headache]

16 hours ago, Lithopsian said:

Get the diagnostic output and it will either tell you why it is over-fuelling, or tell you that it doesn't think it is.  If it doesn't think it is, then that points to an injector or fuel pressure regulator problem.  Or if you're really unlucky, bad inputs that are hard to spot like a vacuum leak or MAP sensor on the fritz.

Could I check it if I see the values of the ECU or it's needed to take it to a professional? If it's over fueling, it's because it needs to fix the engine map? 

And related to the vacuum leak, any place to star checking if the fuel pressure regulator is okay? 

[Lithopsian]

Emerald have their own software for reading (and writing!) info to the ECU.  Making sense of it all might not be so easy!  I don't have an Emerald so I can't really give you a lot of detail.  I'm slightly surprised that your garage seems to be just randomly replacing stuff and not fixing the problem.  One fun thing is that Emeralds are often installed to piggy-back, keeping the original MEMS ECU as well, easier to install but harder to diagnose.  So you might want to check that first.  Here's a page you can start looking at:

https://www.emeraldm3d.com/software-manuals

I doubt that you need a different engine map for the over-fueling.  It was doing it before you had that ECU, right?  More likely some input to the ECU is throwing it off.  Could be everything is perfect and excess fuel pressure or faulty injectors are just pushing out more fuel than they're being told to, but that wouldn't be my first guess.

Finding vacuum leaks isn't easy, probably best to see what the diagnostics say first.  You could have a quick look for any split or cracked hoses, but it could be out of sight, or somewhere tricky like the manifold.  You can test fuel pressure if you have a pressure gauge; just plug it into the fuel feed hose and see if you get to 3.0 bar and no higher with the fuel pump running.