140 Sigma Supersport cold running?

[johnL]

Hi All

New to the club and this is my first post. I have a 140 Sigma Super sport, bought from Caterham Gatwick in March this year. We have had quite a few issues with the car and it has spent quite a lot of time back at Gatwick as well as others being sorted (Thundersports, DPR and PGM all of these guys have been fantastic).

Dealing with Caterham is like pulling teeth and I am slowly loosing patience dealing with them.

The issue I have now is when I start the engine from cold it runs okay for about 15 seconds, then starts to hunt up and down on idle until it no longer runs, restart and hold the revs on the throttle at about 1100-1300 RPM for a few minutes then it seems fine. It has started doing this since we have been having the colder weather.

Now is this normal for the 140's or is this looking like another visit to Gatwick?
 

[Jonathan Kay]

Welcome and Happy Christmas.

Where are you?

Private Message sent.

Jonathan

[ChrisC]

I think it’s normal behaviour for a lot of the current Caterham models, but I don’t think it’s by design.   From what I can tell Caterham use manifold pressure over throttle position sensor (TPS) to maintain idle because the ECU does not learn TPS position, which for the most part works, and all cars run using one setting.  However I have found sometimes it’s not prefect and  the odd tweak can really help, the strange thing is closing the throttle slightly and drawing more vacuum helped the ECU detect idle easier on the two cars I have had with this problem.  However make sure your ECU isn’t powered when you make throttle position changes, easy to do if you have an isolator fitted, if not you will need to disconnect the battery each time because the ECU is permanently powered.

[johnL]

Hi Jonathan

 

I'm in Redhill, Surrey the car is now in Biggin hill for a couple of months for the bad weather in a garage.

Chris, would changing the TPS affect the warm engine running as the car runs fine once it warms up, just in the cold weather when first started it has this problem?

[K7 VCT]

May be call sevens and classics for advice, as you aren't to far away from them.

[ChrisC]

The adjustment I have did on a couple of cars now, didn’t effect the warm running, but basically helps the ECU know when to idle, by increasing the vacuum.  On my car I did try to see how I far I could go, and eventually the throttle is so closed the idle can’t be maintained.  It’s only a single screw so you might as well have a play, just remember where the original position is, and disconnect the battery as you do it.

[pugwash]

Hi John,

I have a Supersport 140 that I built in 2012 and has a full CC service history.  Mine has always behaved as you describe.  Sometimes the hunting gets to the point that the engine stops and I just restart it.  CC have adjusted it over the years so it will start and run while hunting without stalling.  After a few mins it ticks over smoothly so I have never really worried about it.  

I just put it down to part of running a Caterham.

regards,

Mark.

[L777JDP]

Hi John,

From the comments I wonder if it is not an issue with the CC ECU. I had my engine upgraded by Stuart at Premier Power, including a new ECU. While I did not have any starting problems prior to that, the new ECU is programed to run with higher revs for a few seconds after starting before dropping back down to normal idle speed.

You may want to see if you can get the CC ECU unlocked and reprogrammed as I struggle to imagine that multiple cars have the same fault unless it is a software/programming fault. Not sure who might be able to help with that, but doubtless others on here will have experience. PGM are excellent but not sure if this is up their street.

Best regards,

John.

[ChrisC]

I don’t think there is anything wrong with the ECU or the map that CC provide, it’s just a one size fits all (nearly) without any learning features approach.    You can’t compare that to the custom work Premier Power produces, or getting a custom map done at Road and Race using the original ECU.

[Tom_Arundel]

The throttle pot. setting is incredibly sensitive to position and voltage at closed throttle and does give your symptoms. At a minimum it requires Easymap and a lot of tries to get it right but it can be done and is `sweet` when achieved.

Where are you?

[SM25T]

ChrisC .... Track n Road maybe ... not Road & Race.

[SKC]

Hi All,

Happy New Year.

It's a calibration issue with the cold start map in the ECU.  Caterham will run a basic calibration / map for all vehicles that are the same spec, ie Sigma Supersport.  Small adjustment of the throttle pot and idle screw may improve cold start but as is often the case, if the cold start is improved, then when the engine is up to temperature, you'll sometimes find the idle speed is too fast.  I'd look to get the idle speed right when the engine is hot and then see what it's like when it's cold.

Regards

SKC