16 replies to this topic

[ings]

Hi everyone,

I’m having recurring problems passing the emissions test with my Mini and was hoping someone might have some advice.

My engine setup is as follows:

• 1310cc engine

• HIF44 carburettor

• Big valves head from minispares

• Evolution camshaft

The problem is that my CO₂ readings are consistently too low during the emissions test. I can easily adjust the CO values using the mixture screw on the carburettor, the engine runs fine at lamda 1 but no matter whether I set the CO to 1% or 3%, the CO₂ reading stays around 8–10%. The HC is around 1000

I need to achieve at least 11.5% CO₂ to pass the test.

Has anyone experienced a similar issue with this kind of engine setup? Plugs, are new and gapped. valve clearance is also perfect.

Could the camshaft, carburettor setup or ignition timing be responsible? Or should I be looking at something else?

Any advice or suggestions would be greatly appreciated!

Thanks in advance!

 

 

[68+86auto]

Fixing the HC issue will almost certainly fix your CO₂ issue. 1000ppm HC is massive, even 500 is high.

 

Do you know the O₂ reading? That will help determine the fault.

 

At this stage with the information available, I would say you've got an ignition issue or a worn engine.

 

What do the four gas readings do at say 2500rpm?

 

 

Have a read of this and the linked pages: https://www.crypton..../emissions.html

Edited by 68+86auto, 12 October 2026 - 10:57 PM.

[ings]

i just have the lamda reading so this is actually the oxigen right?

The engine is freshly rebuild last year and has around 5000KM.

 

Ignition timing is set at 10°, NGK BP6ES sparkplugs, CSI distributor with vacuum, 3ohm coil and new leads...

[68+86auto]

i just have the lamda reading so this is actually the oxigen right?

The engine is freshly rebuild last year and has around 5000KM.

 

Ignition timing is set at 10°, NGK BP6ES sparkplugs, CSI distributor with vacuum, 3ohm coil and new leads...

 

Lambda is a calculation of multiple gasses so is of little diagnostic value. It cannot establish between a leak, lean mixture or a misfire. Lambda is only good on a perfectly running engine which your one isn't.

 

So you don't have the readings for all four gasses during the emissions test?

What gap did you set the plugs at?

How is your breather system connected?

 

What is the voltage at the coil positive terminal with the engine running?

 

There are so many possibilities so it is hard to say anything without being there and having the appropriate equipment.

 

Without a gas analyser, you'll never know if it is fixed. If the CO value you said was based on converting from Lambda, it is possible that it is actually running lean. Maybe you should set the mixture using the peak rpm method.

Edited by 68+86auto, 13 October 2026 - 12:43 PM.

[ings]

The O₂ level is 1.9%.

I have the spark plugs gapped to 0.8 mm.

At 780 RPM, I measure 13.5 V at the ignition coil. At higher RPM, the voltage reaches a maximum of 14.1 V.

I’m happy to hear any suggestions. Even with all the tools available and standing right in front of the engine, it’s not easy to pinpoint the problem.

[cal844]

You ideally need to get the car on the road to see what the spark plugs are telling you.

[ings]

The car is on the road and the spark plugs looking good they are grey white…

[68+86auto]

The O₂ level is 1.9%.

I have the spark plugs gapped to 0.8 mm.

At 780 RPM, I measure 13.5 V at the ignition coil. At higher RPM, the voltage reaches a maximum of 14.1 V.

I’m happy to hear any suggestions. Even with all the tools available and standing right in front of the engine, it’s not easy to pinpoint the problem.

 

Ok so if the O₂ is 1.9%, I would consider that ok. Many charts will say that is excessive but I find that to be normal.

 

What you are saying is you have:
CO: around 1-3%

CO₂: 8-10%

HC: 1000ppm

O₂: 1.9%

 

HC is clearly an issue and I believe it is an ignition issue but there is a possibility that there is a compression/cam/valve related issue.

 

If you ask me, the plugs should be set at 25 thou with that ignition system. In my opinion, your ignition system will actually have lower output than with points.

Does it have vacuum advance and is it connected to the manifold or is it ported?

 

 

I know how I would diagnose it but unfortunately you won't have the equipment available to do so.

 

Even with all the tools available and standing right in front of the engine, it’s not easy to pinpoint the problem.

 

The tools do exist to make this an easy job. It just isn't something that the average person is going to be able to acquire or know how to use.

Edited by 68+86auto, 13 October 2026 - 11:34 PM.

[timmy850]

What kind of inlet manifold is it? Are you able to hook up water heating to it?

Does your distributor vacuum give advance at idle? If you have full manifold vacuum and excess advance at idle it can affect emissions

[coopertaz]

don't know the rules in your country but in the uk you can test at fast idle. have had issues myself with the minispares evolution cam on my 1340 it would pass at fast idle but needed valve clearance upping to 20 though before it would pass at idle. engine was not worn and had no other issues. hope this helps

[68+86auto]

don't know the rules in your country but in the uk you can test at fast idle. have had issues myself with the minispares evolution cam on my 1340 it would pass at fast idle but needed valve clearance upping to 20 though before it would pass at idle. engine was not worn and had no other issues. hope this helps

 

I too was thinking about the cam and it is one reason for wanting a high speed reading. I think that if the cam was the issue, it should also increase O₂.

[ings]

In Switzerland, we only test at a maximum of 800 rpm. Fast-idle testing is not permitted.

I have a Minispares alloy Torquemaster inlet manifold with water-heated ports, but I’m not using the water heating since I usually drive the Mini only in warm summer temperatures.

The CSI distributor is connected to the vacuum port on the carburettor. When I disconnect the vacuum line, I can see the readings getting worse, so I assume the distributor is working as it should.

The valve clearances are set to 0.017". Minispares states that this camshaft should produce very low HC emissions.

 

[timmy850]

From what I understand you’ll get more “vaporised” fuel if you use the water heating on the manifold. It’ll mean less fuel droplets and it’ll potentially give less raw fuel out the exhaust

I’ve added the water heating to mine recently

Water heating the manifold is a good option for a road going car that needs to pass emissions (just like a high power ignition system and vacuum advance) and have a long service life

[ings]

I’ll hook up the heating manifold, set the valve clearances to 20 thou, and gap the spark plugs to 25 thou.

I can’t run a hig power ignition, as CSI clearly specifies that the coil must have a minimum resistance of 2.5 ohms. Using a lower-resistance coil could damage the digital distributor.

 

 

[timmy850]

It makes me wonder why they make such a fancy distributor and then only make the module powerful enough for a weak 3 ohm coil?

Theoretically a variable dwell system with a 3 ohm coil will make less power than points at lower rpm. Coil power is another key component for passing emissions