Caterham Supersport 'Running Rich' (Lambda Sensor Issues)

[Ben_Robinson]

Good afternoon Everyone,

I've not posted on here before on account of my 7 running sweet as a nut, until a month or so ago.

I have the Supersport 140, 1.6 Ford Sigma engine.

I had noticed on the odd run out the car sounded like it needed to clear it's throat for want of a better explanation. Rather than the usual steady engine purr as I pressed the throttle or a nice tick over when holding the throttle steady, the sound was very gurgled and bouncy.
Sometimes it did it and sometimes it didn't.
With a house move the car was in the barn for a few months.
When I took it out again the same thing happened, unable to hold a steady throttle, stalled at junctions if I did not dip the clutch and increase the throttle, generally a horrible noise.
When I got home from this very short run the catalytic convertor was glowing bright red.
I managed to limp down to the local mechanics a few days later (stalling most of the way, the car sounding like a cross between a V8 and an old tractor)
The mechanic plugged into the car but could not get his system to talk to the ECU (he tried various different engine types)
If you put your hand over the exhaust it quickly becomes black and wet.
The mechanic suggested the car is 'running fuel rich'
He thought I might try replacing the Lambda sensor first; if that does not work then try replacing the engine coolant sensor; if that does not work seek advice from Caterham he said.

I'm a little perturbed about buying part after part in case they don't work.

Would anyone out there be able to point more directly to a possible issue or resolution?

Thanks in advance.

Ben.

Edited by Ben_Robinson on Thursday 13th May 15:53

[Tupwood]

Hi Ben,

You may be lucky, but I think a query of this technical nature would be better posted on the Lotus Seven Club website – are you a member? There are also some Facebook-based Caterham technical sites you can try (but answers may vary).

Personally I would be looking for a local Caterham specialist to diagnose the car in more depth. There are some great independents around, plus regional Caterham Dealers… where are you based?

My car is a K-Series, so I'm not much use on Sigmas, sorry.

[DCL]

Won't be lambda or coolant - I'd put my money on TPS, but if the cat is getting red hot then you could be burning oil. Does it start OK? Any smoke?.

[agatebox]

I’m afraid you need to find s local Caterham owner with a copy of Easimap and the necessary connection lead required to interrogate the ecu. Then you’ll be able to identify which if any of the sensors are causing grief. If you buy a replacement TPS sensor you’ll still need Easimap to make sure it’s set correctly, or any other replacement sensors are functioning as intended.
As a complete stab in the dark (and cheap) you could get hold of a used identical lambda sensor from a breakers off eBay and swap it out since its a five minute job, though obviously if the lambda wasn’t the problem in the first place......
From experience a faulty/non-working lambda can make the car virtually undrivable, drink fuel like a fish and sooty as hell but there could be other factors in this case.

[Ben_Robinson]

Many thanks for the pointers folks, very helpful and muchly appreciated. I'll let you know what it turns out to be.

[Kenty in Weardale]

When my Lambda failed (2014 1.6.Sigma 270) there were no symptoms at all until it came to MOT time when it failed catastrophically on the emissions; hope this helps