Erratic tickover

[AlanO]

270 R (2020 build). Help please. All's fine and dandy until its run for an hour or so and then the tickover starts to play up. Normally it's at just over 1000rpm but after a longish run it climbs to 2000rpm. Flicking the throttle takes it back down but invariably it climbs again. It occasionally cuts out completely when stationary and on other occassions it 'hunts' (pulsing between 1000 to 1300rpm) when stationary) It runs at steady 80°. Any clues please. Thanks.

[Mrb00ns]

The standard mapping is a dog, in my experience. Get it remapped and it will run like a treat. 

[timb2117]

Just a hought, double check the throttle cable is well lubricated and moves freely and the throttle butterfly same and the stop that it returns to has not been moved or gone out of setting.

- Very long shot as I dont think it would cause all those symptoms but you never know and its free to check, good luck.

Tim

[SM25T]

Could also be the tiniest air leak on the inlet side.... Look for a split in an air hose around the inlet manifold.

[AlanO]

Helpful thanks. I wondered about remapping as have checked throttle action. Will investigate for air leak and see how it goes on F&C run.

[Dixa1225]

Check the TPS setting.  You will need Easimap & the cable to check.

[AlanO]

Thanks. You've set me off reading past blatchat posts and learning TPS settings! https://www.caterham7diaries.com most helpful!!

[MTW]

I had hunting and irratic idle when warm and it turned out to be the O2 sensor, after it was replaced the car runs great (as great as the standard map allows) again.

[AlanO]

Just by way of an update, mainly in case others have similar troubles...

The car got worse on the way to Aberdovey, hunting or fluctuating tickover, cutting out every time the car stopped etc. Well last nights bedtime reading of past Blatchats and a couple of useful blogs suggested first trying the 'throttle reset'. (Ign on, 5 slow full depressions of the accelerator, ign off. Then start). We'll I'm pleased to say that it did the trick and we drove home without incident and the car resting and a nice gentle idle at lights etc. Many thanks! 

[Jonathan Kay]

Well done.

Thanks for adding the solution.

Jonathan

[StevehS3]

Great that it is sorted but can a Sigma (with MBE ECU) have the throttle position set using that process? It looks very much like the way a K with standard Rover ECU is done.

[Dixa1225]

The method described is for a K series. This is not applicable for a Sigma engined car. Pure chance this has cured the problem. 

[GulfSeven]

It requires Easimap, an MBE cable and getting under the bonnet with tools on a Sigma unfortunately.

Perhaps depressing the accelerator pedal lots freed up the cable?

[StevehS3]

I was thinking that, It is always good to take it to the floor on a regular basis ;-)

[AlanO]

Well it worked for me! I'd previously opened the throttle in car and by hand 'under the bonnet', checked its  physical peration etc with no improvement so I'm bewildered by your thoughts. Anyway cars back to normal and I'm a happy bunny. Cheers.

[AlanO]

Well it worked for me! I'd previously opened the throttle in car and by hand 'under the bonnet', checked its  physical peration etc with no improvement so I'm bewildered by your thoughts. Anyway cars back to normal and I'm a happy bunny. Cheers.

[aerobod - near CYYC]

One other thing to check on the Duratec that can cause uneven idle due to the throttle blade not returning to the stop correctly, is that the throttle body to air filter Jubilee clip isn't overtightened. If it is and depending on temperature variation, it can cause slight jamming due to throttle body distortion.

[Tom_Arundel]

Don`t start up with your foot on the throttle, it confuses the ECU.

Watch out for overtight TPS mounting screws stopping throttle return

[AlanO]

Thanks Tom, putting my foot on the throttle at start up is something I may habe inadvertently done. Very difficult to get out the habit! 

[aerobod - near CYYC]

With the MBE ECU, there isn't any standard throttle calibration done at startup (throttle site is set purely by TPS voltage when at the stop and the specified voltage at full throttle, then mapped on a static curve between the two), so I don't think having a foot on the throttle when staring the engine will have any adverse affect on how it runs. It shouldn't be necessary to use throttle to start the car, though. When I put in an unlocked 9A4 ECU it initially had sub-par mapping when cold and required throttle to start it, but that had no adverse affect on how the car ran after it had warmed up a bit.

[ScottR400D]

Looking back at the original post, the worsening tickover getting worse as the car warms is not what most see from poor set ups is it? Generally things improve as the engine warms. 

I wonder if that does point to a mechanical issue, any one of those indicated along the thread, and the 'solution' is just a coincidence. Time will tell I guess. 

[StevehS3]

I agree. It seems that fully depressing the throttle several (5) times in succession cured the problem. I have been thinking something might have been sticking such the throttle or the cable.

[AlanO]

I'll update as time goes on or if the problem reoccurs. Just to recap, the problem worsened the longer the run rather than when it attained a certain temp. (Beyond an hours running or so). Anyway, the 5 depressions may well have cleared a mechanical problem rather than reset the ECU and given what I now know I'll first check mechanical issues if it reoccurs. And the experience and your comments have been most helpful. Thank you!

[ScottR400D]

I think some of these cars can continue to warm through for quite some time (and distance!). 

It's just that most people report erratic idle and throttle issues when just started, improving as running time and temperature increases. 

Anyway, it's good that the car's running well now and you've got some ideas should the problem return. Fingers crossed it doesn't!!

[AlanO]

I'm revisiting this thread as I still have a tickover problem, although slightly different..

The tickover became more erratic and on the F&C run it continually cut out at junctions/light etc (it would die as soon as revs settled at about 1,100rpm).  It started fine following each cut out but wouldn't tick over.  The cutting out was solved with a change of lambda sensor but now the tickover settles at anything up to 2,000rpm.  I'll pull up at lights for example, and it'll be revving away.  At cold and until run for 30mins or so it ticks over fine and settled at about 1,000rpm.  It has a locked Caterham ECU.

Do I:
a) Download Easymap, buy a cable and try to identify the issue? (I'd learn a bit about the car more but may not actually be able to fix the problem, or
b) Get it back to Caterham who 'should' be able to fix it, or
c) take it elsewhere? (where? I'm in Hertfordshire)

Cheers.