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I'm not sure those are the right plugs. Which ones came out? I think VVC will be wasted spark so you need BCPR7ES or NLP100290 or I'm currently using Denso K16PR-U11 which also seem fine.

This image is stolen from Umicore. It shows that a common three-way catalytic converter needs to be very close to lambda 1 for best efficiency of all 3 conversions. Below lambda 1 (running rich) the ability to reduce HC and CO drops off rapidly. It may still be reducing NOx levels but those aren't checked on the MOT.

The only important thing to take from those results is the lambda values - it's running very rich for some reason. Until the lambda is within range the cat won't be functioning anyway so you can ignore that for now. Sorry I don't know the sigma engine very well but I would start with checking the lambda sensor, coolant temp sensor and throttle position sensor.

I recently had a problem with the alternator warning lamp started flashing on and off regularly when the engine was running regardless of rpm. It still seemed to be keeping the battery charged at just over 13V. I have replaced the alternator, and I now get the warning light staying on constantly when the engine is running - although not as brightly as when the engine is stopped. The new alternator is still charging the battery (now closer to 14V) and I have no other electrical problems. Do you think this issue is related to the above? EU3 K series with standard tacho. Thanks.

Just to update this.. I must say I had fantastic service from QED and Jenvey. I sent the throttle bodies back to Jenvey and within a week they had sent back what appears to be a brand new pair. I have fitted them and the noise seems to be slightly reduced but still present. By lowering the idle speed I could get rid of the noise completely at idle but it's still present at very light throttle just above 1000rpm so not a complete solution. I think I have to put it down to a characteristic of the engine unless I can find another solution.

Great photos. Thanks Dave!

That's really good to know, thanks. Out of interest what sort of mileage did yours do before you rebuilt them?

Thanks, that's what I'm thinking too. It's very good to know it's not something inside the engine going wrong but still a bit annoying that I can't easily stop it. If it's not normal, I wonder if the throttle bodies are serviceable.

That's interesting Revilla. I did wonder if it could be some sort of combustion still happening when the intake valve opened. But in my case it's very regular and I couldn't see any flashes around the butterfly. I took a quick video showing what happens when I press on the end of the butterfly shaft

For a while I thought it was the injectors but using a screwdriver to my ear on them I couldn't pick up the same noise. Also I swapped the injectors around and the noise still seems to be coming from the front cylinder. I'll do some more investigating today.

I've been chasing an annoying ticking noise coming from the engine at idle and on overrun below around 2000rpm for a while now. It's most noticeable when the engine is up to temperature and everything else has quietened down I suppose but it's very noticeable from inside the car and really quite loud when standing near the front of the car. It's a k series with forged pistons and Jenvey (QED) DTH ITBs and the engine runs fine but I keep expecting this noise to turn into something much worse! Anyway I've finally narrowed it down to the front cylinder on the intake side. And after more playing around I found that the noise would stop if I pushed on either the centre of the butterfly shaft (pushing towards the engine) or pushing on the end of the shaft (pushing towards the back of the car). It seems like such a small amount of movement of the shaft when I do this that I'm amazed this is causing so much noise. I wondered if anyone else has seen/heard this and if anyone knew a solution to permanently stop the loud rattle/ticking noise? The throttle bodies were fitted new about a year ago and I think the noise has been there from the start it's just taken me this long to work it out.

Hi Rich, Yes the pistons are still available. I've updated the first post to show which bits have now sold. Thanks

David that's the best explanation of the workings of the ATB that I've seen - thanks!

Hi Jack. Sorry, I don't know on that one. It was supplied with Jenvey DTH throttle bodies so I suspect not but can't say for sure.

Yes you can PM sent

Having a clear out of engine parts that I collected and no longer need. Collection from Daventry preferred. Pair of used Piper 633 Camshafts, used for no more than 1000 miles - SOLD Single used Piper BP285H camshaft, unknown usage but looks to be in good condition - £150 Distributor rotor drive used but I believe it can be refitted? - £5 Pair of Piper vernier pulleys (black), used but in very good condition - SOLD Set of MaxSpeeding 1.8K forged con rods complete with ARP bolts and assembly lube, boxed and unused - SOLD Jenvey aluminium fuel rail with fasteners, new and unused - £40 Set of used Omega forged pistons (80.0mm), unknown usage but have been checked over by Knight Engine Services and measured (sizes written on underside). No issues found. Complete with rings but require circlips and possibly new gudgeon pins (available from Omega) - SOLD 52mm throttle body, used - SOLD Hopefully photos are visible here: https://photos.app.goo.gl/ffo6eKgr3fmamfC3A Thanks, Matt.

I can also recommend R-Tech. I've got the TIG welder linked above as well as a MIG from them and they've been very good. The warranty and UK support is a big bonus. They're not the cheapest but if you're not interested in welding aluminium then you would only need the DC version which is about half the price of the one above.

Those tyre ratings are interesting, I would like to know how they're tested. I understand it only looks at wet braking distance but even so, a B rating for what is essentially a semi-slick is impressive. I expect they are tested on a much heavier vehicle than a Caterham so maybe that helps the Nankangs? They were definitely NS2Rs that I used. One thing to note though is that there seem to have been 2 or more different compounds available for the NS2Rs. Looking back at photos mine had 'Treadwear 180' written on the sidewall which I believe is the 'road' spec and hardest of the compounds. I expect a softer compound (if still available) would suit the Caterham better. Anyway I'm interested to hear how you get on with them. For the R888Rs, cold pressures of 16-18psi are what I use as well.

Hi, I have used both on track and road albeit in 13" size. On a dry track the NS2Rs were great and I marginally prefer them to the R888Rs. I found the stiffer sidewalls on the NS2Rs gave really good feel. Peak grip was similar between the two maybe just slightly better on the NS2Rs once they were fully up to temperature. However - the R888Rs are miles ahead when it comes to cold and wet performance. The NS2Rs took a good half a lap on track to get any decent grip out of them and therefore they never got up to working temperature on the road. Whereas the R888Rs are great from the moment you set off and surprisingly good in the wet too. For me if you are using them on the road at all then the extra cost of the R888Rs is well worth it. If it's for (dry) track only then the Nankangs are great.

I'm experiencing similar symptoms of a clattery noise under hard acceleration (1.6 K). Sounds like it's coming from the top of the engine on the intake side. I can't replicate it when stationary. I got carried away over the winter and made quite a lot of changes but it seemed like the noise started when I changed the exhaust manifold (from standard short 4-1 to a 4-2-1 modified to keep the standard silencer). I only gave it a quick test before stripping it down again to change the pistons and head (upgraditis) but I believe the noise was there at that point. I initially thought it must be an exhaust leak or the primaries touching the chassis but I've triple checked for leaks and reassembled with high temp silicone. No sign of anything touching the chassis and it sounds more like its coming from the intake side rather than exhaust. So now I'm considering the fuel system. I've tried different injectors and a different fuel pressure regulator with no improvement. I guess there's no easy way to check the fuel pump is working properly in order to rule that out? Would be good to know if Ozzy managed to sort his issue out but it looks like he's no longer active here.

Dave, will the new kits be available to buy from yourself or eliseparts.com? (or both?) Did you get any photos during the trial? Thanks.

Hi Both. Thanks for the replies. When I first had the issue I did check the error codes and I had: - Oxygen sensor heater circuit malfunction (P0135) - Misfire detected with low fuel (P0313) If I manage to get a live scanner then what should I be looking for with the lambda sensor reading? Am I right in thinking the reading should sort of oscillate in normal conditions? I'll check for exhaust leaks as well but I definitely can't hear anything unusual. The car is a standard 1600 k series and it's got the short 4-1 manifold with the sensor just after the collector so it's reading all 4 cylinders. Andrew, do you have more info on the light bulb test? Does it need to be a certain type for the ECU to send the signal and should it start pulsing straight away when the engine is started? Thanks again!

I have a 2001 1.6 k-series (EU3) Caterham and I'm having some issues with the engine misfiring due to the lambda sensor. It seems to be a problem with the heating of the sensor. The misfire is only present at low load, at higher loads it runs fine presumably because the engine is producing enough heat to get a proper reading from the sensor. With the sensor disconnected the car also runs fine which is how I've been using it for the past year or so but I thought it was time to get to the bottom of the issue. I have tried replacing the sensor but still have the same issue which leads me to believe it's an issue with the wiring. I then thought it could be the MFRU causing the problem but I was recently reading the article on the starter motor 'k-click' problem (another thing I need to fix) which states that the oxygen sensor relay in the MFRU is not used on a Caterham. Looking at Revilla's excellent wiring diagram and seeing as everything else is working properly then it looks like there are only two wires which could cause it. And if it's not those then it points towards an internal ECU problem? Has anyone else had this issue? Any other ideas? Thanks!