Area Representative Nick Chan Posted August 28, 2010 Area Representative Share Posted August 28, 2010 My Sigma car (1600/125 bhp Academy) was running as smooth as usual at a recent Curborough practice day for the morning session but in the afternoon developed a misfire after coming back off a run. It hadn't been off track and after a quick inspection nothing seemed to have dropped off or come adrift but the car was left for the remainder of the day. Investigating later on, the car starts but only with coaxing from the throttle and was running on 3 with No.4 being stone cold. Checked plug in No.4 in another lead and its fine and also fine in the HT lead for No.4 so put plug back in and the car starts on all 4 but still has a misfire. Its running very rich and throwing out lots of black stuff from the exhaust. Re-visiting it today (with a hope of sprinting tomorrow at Curborough!), tried to run it and now its No.1 that doesn't run. Took plug out and cleaned it and put it back and its back to running but the misfire is still there with the very rich running. I have checked the obvious connections to make sure things are pushed home and re-cleaned the engine earth from chasssis to engine mount that is criical with the car but it still remains the same. Anyone have any other suggestions that I can check or is it off to a diagnostics place as it might be ECU related given the car starts and runs on all 4 but is obviously over fuelling right from the start? PS Curborough is off the cards for me entering but at least I get a good chance to watch the others in Class 1 Nick Back in a BEC! - but done alright in Class 1... Link to comment Share on other sites More sharing options...
Z3MCJez Posted August 28, 2010 Share Posted August 28, 2010 Is the little air pipe back to the ECU still in place? I'm not syre it will be the cause of the misfire, but the very rich running is a symptom, which may have fouled the plugs ... Jez Link to comment Share on other sites More sharing options...
Area Representative Nick Chan Posted August 28, 2010 Author Area Representative Share Posted August 28, 2010 Hi Jez, I'll check the pipe. Is this the one that goes down under the TB and looks to be a breather? I think it should be something simple (or maybe should that be "hope") as it was running exactly as usual earlier on the runs. The misfire could easily be the plugs fouling really badly as they were all sooted up when I checked them despite the others having run Nick ----- Back in a BEC! - but done alright in Class 1... Link to comment Share on other sites More sharing options...
elie boone Posted August 28, 2010 Share Posted August 28, 2010 My guess is that it's the coil if the misfire changes from cil 1 to cil 4, if i am right that it's wasted spark Link to comment Share on other sites More sharing options...
The Pikey Posted August 28, 2010 Share Posted August 28, 2010 Hi Nick couple of thoughts.. TPS failed? Lambda sensor failed? Your lambda lead was not secured last time I saw it so could it be a wire broke? cheers Jason Link to comment Share on other sites More sharing options...
huwp Posted August 28, 2010 Share Posted August 28, 2010 Had a similar problem on my Sigma recently. Tracked down to a failed Lambda sensor. The biggest PITA was the fact that only CC can access the ECU so I had to have my car trailered to Caterham Midlands to sort it out. Car had only done 7,000 miles and comes on top of many many other woes..... Huw Link to comment Share on other sites More sharing options...
Area Representative Nick Chan Posted August 28, 2010 Author Area Representative Share Posted August 28, 2010 Thanks for the replies. I had a good look at the air pipe from the box by the ECU and it had a tiny split in it so I have taped it to see if it makes a difference but it doesn't. I think the car is having a laugh now as No.3 is not firing and the other three are... Jason - I have checked the wires and all seems fine (to my visual inspection) Huw - what were the problems with your Sigma? Was it simple rough running or have you experienced the car firing on 3 cylinders only until you cleaned the plug? Nick ----- Back in a BEC! - but done alright in Class 1... Link to comment Share on other sites More sharing options...
Z3MCJez Posted August 28, 2010 Share Posted August 28, 2010 Nick - Only just back to this. If the pipe was split you will have furred up the plugs. I suspect you may now need to clean thoroughly, or replace, and replace the pipe at the same time. I had that pipe replaced after only a year, as it was already starting to degrade. As an aside, there is a catch tank option now available to prevent oil being fed into the air intake, and to try and keep oil out of the cat. Your problem doesn't sound like this would help, but if you are sprinting the car then it might be worth looking at it. Jez Link to comment Share on other sites More sharing options...
huwp Posted August 28, 2010 Share Posted August 28, 2010 Nick, the car was ok when cold but developed a terrible miss-fire when warm. It made the car undriveable. The Lambda failure was diagnosed via the ECU. I am interested to read about the degradation of the pipe to the ECU however and will certainly check that out as I sensed recently that the car was hesitating again. Feel free to ring me tomorrow if you want to discuss further 077 99 33 8404. Huw Link to comment Share on other sites More sharing options...
Windy Corner Posted August 29, 2010 Share Posted August 29, 2010 My Sigma 150 killed a lambda sensor at Curborough recently.................. Rik Roadsport SV 1.6 Sigma 150 in Viper Blue here Link to comment Share on other sites More sharing options...
Area Representative Nick Chan Posted August 29, 2010 Author Area Representative Share Posted August 29, 2010 Hi Rik, What were the symptoms of your car having a fault? I have had a bit more thought about it and the first indication of a problem was the car hunting when it was ticking over. Normally it sits perfectly on a tickover of 1k and has sat like that for ages when waiting for the sprint run to start or generally warming up. On Tuesday, it started to hunt, nearly cutting out and then back to 1k and so on. Now I have got the plug fouling issue which means it doesn't run without me revving it and now it just cuts out when I stop revving it. I'm sure its a sensor but which one? More investigation needed I think... ----- Back in a BEC! - but done alright in Class 1... Link to comment Share on other sites More sharing options...
Windy Corner Posted August 30, 2010 Share Posted August 30, 2010 Nick, Almost exactly as you describe, fouled plugs, wouldn't idle, ran very roughly, would misfire to the point it was undriveable. Coaxed it up to CCM and soon diagnosed as Lambda via the ECU. Not that you needed the lappy to diagnose, it, Nick was almost spot on as he heard it kangaroo up the drive at CCM............ £230 notes later............ Rik Roadsport SV 1.6 Sigma 150 in Viper Blue here Link to comment Share on other sites More sharing options...
TobyCoulson Posted August 30, 2010 Share Posted August 30, 2010 My Sigma 150 was playing up and wouldn't run smoothly until warmed up. A loose TB was found to be the problem. A cigarette butt placed beneath a Band-Aid makes a cheap nicotine patch Link to comment Share on other sites More sharing options...
Area Representative Nick Chan Posted September 4, 2010 Author Area Representative Share Posted September 4, 2010 Bit of an update on this problem : Taking on board the comments about the lambda sensor being a potential problem, I did some reading on the web and came across this useful page Lambda sensor problems diagnosis which seemed to tally well with my problems. I bought a new unit from Euro Car Parts (their part number 710590180 and originally manufactured by Bosch for Ford) for £33.56 plus VAT with some cat cleaner (fuel additive to clean the crap out of the catalytic convertor), and despite it smoking a bit to start with, it is much more crisp when being revved than before.... but I still have the poor running and very lumpy tickover ☹️ I think I am going to have to get the MBE ECU interrogated so I can see what's causing the problem. And so it goes on 😶🌫️ Nick BTW Toby I tried shaking the TB and it seems securely in place Back in a BEC! - but done alright in Class 1... Link to comment Share on other sites More sharing options...
Area Representative Nick Chan Posted October 10, 2010 Author Area Representative Share Posted October 10, 2010 Hi Guys, Finally had a chance to look at the Sigma today (nice weather, MBE Can adaptor to be used and with Richard Price's help) and the fault was the air pipe that Jez had suggested. It had split on one end and fallen off the plenum on the other! Strange though how this caused two cylinders not to fire at all today though. Whilst the car would run and tickover smoothly immediately after start up, the Easimap software showed the car was running on some type of cold start map for the first 30 seconds and then this would time out, the lambda readings would change and then the car would die. This happened repeatedly so we changed back to the original Lambda sensor which I had thought was faulty but improved the situation as the car would idle now after the initial 30 seconds albeit a bit lumpy. Taking the car out for a quick blast (the first one since the end of August ☹️) seems to have it running as before so big thanks to everyone for their suggestions and especially to Richard for his help (again!). Its good to have it back again 😬 Nick Back in a BEC! - but done alright in Class 1... Link to comment Share on other sites More sharing options...
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