Bokonon Posted August 24, 2014 Share Posted August 24, 2014 I've had my car for a couple of weeks now and it's been running beautifully until now. It's a 2010 1.6 140bhp Sigma. Was on a long run and noticed it starting to run very unevenly at lower revs. It got worse and worse until it was struggling not to stall at idle with the revs repeatedly rising to 1k, dropping to virtually nothing and then back up again. When driving it was fine above around 3k revs but increasingly badly behaved below that, and was jerky and rough-sounding. At one point I stopped for a few minutes and it was fine again when started for a few minutes, then started to regress again. I have zero mechanical knowledge - is there anything this could obviously be? Edited by - Bokonon on 24 Aug 2014 14:58:07 Edited by - Bokonon on 24 Aug 2014 14:59:39 Link to comment Share on other sites More sharing options...
Grubbster Posted August 24, 2014 Share Posted August 24, 2014 What engine and spec? If on throttle bodies they could be out of balance? Link to comment Share on other sites More sharing options...
Bokonon Posted August 24, 2014 Author Share Posted August 24, 2014 Sorry yes, just edited it :) Link to comment Share on other sites More sharing options...
Grubbster Posted August 24, 2014 Share Posted August 24, 2014 Ah, you added the spec as I was typing Link to comment Share on other sites More sharing options...
John Hughes Posted August 24, 2014 Share Posted August 24, 2014 I would be thinking Lambda sensor. Link to comment Share on other sites More sharing options...
ChrisC Posted August 24, 2014 Share Posted August 24, 2014 I have the MBE lead that might show what's going on. Link to comment Share on other sites More sharing options...
John Hughes Posted August 24, 2014 Share Posted August 24, 2014 I would accept the use of the MBE lead / Easimap. Look for a flat lining Lambda output. I've found the best place for a new Lambda is "Just Lambdas" you need a planar sensor, they had a Bosch on special offer or a Walker one which is slightly cheaper but appears good quality. All you need do is crimp or solder your old plug on. null null Sorry unable to add links when using phone Edited by - John Hughes on 24 Aug 2014 18:37:55 Edited by - John Hughes on 24 Aug 2014 18:40:07 Link to comment Share on other sites More sharing options...
ChrisC Posted August 24, 2014 Share Posted August 24, 2014 I got a direct Bosch replacement from eBay recently, for my cat bypass pipe. Link to comment Share on other sites More sharing options...
Bokonon Posted August 24, 2014 Author Share Posted August 24, 2014 Thanks for the replies so far. Would there be an effect on fuel economy with a dodgy sensor? Appears to be doing about 15mpg currently which can't be right, even with some spirited driving.... Oh, and it does have a cat bypass pipe as well. As I say, it was running perfectly up until Friday though and suddenly started playing up. Was away for the weekend and returning today had to sit in some very heavy stop-start traffic. Pulled over eventually as was having to ride the clutch just to keep it running. Edited by - Bokonon on 24 Aug 2014 21:53:23 Edited by - Bokonon on 24 Aug 2014 21:53:51 Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted August 24, 2014 Share Posted August 24, 2014 If the lambda sensor is faulty, unplug connector in lead. If car then runs fine, sensor at fault. Take number off sensor and order on eBay. Link to comment Share on other sites More sharing options...
ChrisC Posted August 24, 2014 Share Posted August 24, 2014 BM me if you want a look at what the ECU is thinking. Link to comment Share on other sites More sharing options...
Gnockoff Posted August 24, 2014 Share Posted August 24, 2014 If you have only had your car a couple of weeks, have to ask whether private buy or from dealer? If the latter any warranty? Link to comment Share on other sites More sharing options...
John Hughes Posted August 24, 2014 Share Posted August 24, 2014 On a sigma unpluggng the Lambda will not help once the engine is warmed up and the ECU starts to use the Lambda. Fuel consumption will be rubbish as you say. You may have choked your plugs so a new set may be needed. At least you haven't got a cat to knacker Link to comment Share on other sites More sharing options...
Bokonon Posted August 26, 2014 Author Share Posted August 26, 2014 Thanks all, and thanks ChrisC for the offer. Was away yesterday... Will take it to a local place that services Caterhams and see what they say. Need to find a decent place for servicing anyway. Link to comment Share on other sites More sharing options...
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