RyCliff Posted August 18, 2016 Share Posted August 18, 2016 Morning all, hoping someone may be able to help me with a problem that is becoming increasingly frustrating. Over the last couple of weeks, every time I take the Caterham out there have been sudden drops of throttle response when driving along (feels a bit like a misfire but have never driven a car that does so can't say for sure). When I'm out for over half an hour or so this lack of response gets more frequent and longer, until eventually the engine dies out. Then once I've left the car for around 5 minutes it seems to be fine, with very very little to no throttle drops. This happened on an A-road to Wales and yesterday on the M6, the latter occasion prompting me to turnaround and get my daily. I'm surprised as I drove back from Surrey to Cheshire when I bought it with no such problem. The car hunted at idle when I bought it, 1,200-1600rpm which was never an issue. However when this problem is occurring I get no hunting and the car idles at around 1,200 constant unless it's about to cutout. Car was serviced at caterham dealership and I have cleaned the air filter, other than that the engine hasn't been touched in my ownership. It's a 1.4 k series roadsport with a cheesman manifold, k&n air filter and apollo tank being the only engine modifications. Any help on what the cause may be would be much appreciated, as this is starting to get genuinely dangerous. Thanks Ryan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 18, 2016 Member Share Posted August 18, 2016 Could be fuel starvation from inadequate breathing at the tank. The next time it happens take the filler cap off while the engine is still running. Do you hear a rush of air, and does the engine immediately start to run better?Jonathan Link to comment Share on other sites More sharing options...
SM25T Posted August 18, 2016 Share Posted August 18, 2016 Second that suggestion. Link to comment Share on other sites More sharing options...
revilla Posted August 18, 2016 Share Posted August 18, 2016 One possibility is a blocked fuel tank breather. Next time it starts to splutter, remove the fuel filler cap. If you get a whoosh of air being sucked then it goes OK for a few more minutes, that's your problem. Link to comment Share on other sites More sharing options...
revilla Posted August 18, 2016 Share Posted August 18, 2016 Three at the same time! Link to comment Share on other sites More sharing options...
SM25T Posted August 18, 2016 Share Posted August 18, 2016 As a separate issue ... the idle sounds a bit fast too. Have you tried the TPS reset procedure ... if it applies to the 1.4 set up ?? Ignition on ... but don't start the engine. Throttle pedal fully to the floor and fully released ... five times .... just slow and steady. Then ignition off. This teaches the ECU the range of throttle travel. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 18, 2016 Member Share Posted August 18, 2016 Good morning, gentlemen.SNARK!Jonathan Link to comment Share on other sites More sharing options...
TomB Posted August 18, 2016 Share Posted August 18, 2016 The Throttle Potentiomter Sensor (TPS) is resettable on the 1.4. The easiest way I found to reset it was to hand acctuate the throttle quandrant on the engine, from closed to full open, I thought 7 times, that way you know youve got full opening of the throttle. Youll then hear the TPS reset its self with a short whirring noise. That recallibrates the ECU and TPS. It could help and its really quick to do. Alternatively just use your foot as SM25T suggests. But as with the suggestions on fuel tank breathing, it does sound like a fuelling issue. The breathing issue is basically as you use up fuel, unless the tank can 'breathe' to atmosphere, youll create a slight vacuum which prevents the fuel cycling back from the engine to the tank and makes the fuel supply erratic. The main breather is on the right (drivers) side of the tank and is simply some rubber hole, one end connected to the tank, the other open to air. You could simply have a blockage in it. Link to comment Share on other sites More sharing options...
David Brown Posted August 18, 2016 Share Posted August 18, 2016 My future father in law was hugely impressed when I solved this problem on his brand new Princess (car not daughter), having had the problem myself on a Morris 1000. Link to comment Share on other sites More sharing options...
TomB Posted August 18, 2016 Share Posted August 18, 2016 A Morris 1000 with a K series? Ultimate sleeper! Link to comment Share on other sites More sharing options...
RyCliff Posted August 18, 2016 Author Share Posted August 18, 2016 Thanks very much everyone. I'm now up in the lakes without the car so can't have a try, but when I get to the petrol station to refuel there does seem to be a vacuum when removing the filler cap every time. This is no matter whether it's a long or short trip. Im guessing this is all pointing to a blocked fuel tank breather. Thankfully doesn't sound like an expensive fix. Will try the TPS reset too, thanks for outlining the procedure Tom and SM25T. I've got a master battery cut off, will I need to do this with the ignition on? This forum is amazing by the way, there's no way I'd get such a quick response anywhere else! Thanks everyone. Hoping over time I can give the same help to someone else in my position Link to comment Share on other sites More sharing options...
SM25T Posted August 18, 2016 Share Posted August 18, 2016 Hose better than hole !! It could have a one way valve in the breather hose to help prevent fuel leakage. Ensure this is the right way round .... arrow pointing into tank to allow air inwards. Link to comment Share on other sites More sharing options...
TomB Posted August 18, 2016 Share Posted August 18, 2016 You should be able to sort the breather out fairly easily. Take of the fuel filler cover (if you have one) on the inside of the boot to expose the filler pipework connecting the tank to the fuel filler entry. You'll see a couple of small rubber pipes hopefully, one goes to the right down to the gap between the tank and the chassis, the other goes under the boot floor to a breather point on the top of the tank near the level sender. You cant get to this second one easily without taking the boot floor out in my experience. The other one should be ok, albeit fiddly, to take off and check for blockages, this is the pipe where there might be a one way valve to stop fuel leakage in event of a roll over. As this one hangs down, its feasible it could be blocked with road crud, waxoil etc.If your taking it all apart and you havn't a one way valve, it could be worth fitting one and is covered by Caterham Workshop Notice 371. I think Ive got a PDF of it, so will send it you along with the scanned article we discussed. Link to comment Share on other sites More sharing options...
SM25T Posted August 18, 2016 Share Posted August 18, 2016 The small hose that enters the tank at the top front face near the level sender is the fuel return hose from the engine bay ... on mine. Link to comment Share on other sites More sharing options...
TomB Posted August 18, 2016 Share Posted August 18, 2016 Yes, but there is a second breather on top of the tank, from the sender to the filler. You cant see the sender end unless the boot floor is off. Link to comment Share on other sites More sharing options...
RyCliff Posted August 18, 2016 Author Share Posted August 18, 2016 Cheers Tom, for the sake of a few pounds I'd rather fit the valve to save and fuel leakage issues. Might even fix the embarrassing hunting at idle that I can't seem to shift. Never a good look at traffic lights Link to comment Share on other sites More sharing options...
The_ASH Posted August 18, 2016 Share Posted August 18, 2016 I may have this completely wrong but I remember years ago, on Blatchat, a discussion about something very similar, it came down to the fact that the plastic fuel cap allowed the tank to breathe but the aluminium aero cap didn't (or some aero caps didn't), as usual I can't find the thread at present but there was a fix that required drilling the cap in a certain place with a specific drill.The quickest way to check if it's a tank breathing problem would be to wait until the problem occurs and then before you do anything else remove the filler cap, if there is an inrush of air to the tank at that time and the car then works properly once more you have found it or a breather problem outlined in the other posts above. Link to comment Share on other sites More sharing options...
revilla Posted August 18, 2016 Share Posted August 18, 2016 Just one thing to mention that can be slightly confusing here ...Since I fitted the one way valve mod on mine, especially if I run the tank low, and especially on hot days, I get quite a whoosh when I remove the filler cap ... but it's vapour pressure inside the tank blowing out rather than vacuum in the tank allowing air to rush in.It could be quite easy to mistake this for the inrush whoosh caused by a completely blocked vent. Link to comment Share on other sites More sharing options...
RyCliff Posted August 18, 2016 Author Share Posted August 18, 2016 The only way I can think of checking the direction of the air flow is a piece of towel around the filler cap. Is there a difference in sound though? I'm hoping this is the problem but not sure why I don't get the same problem again after the engine has died once Link to comment Share on other sites More sharing options...
The_ASH Posted August 18, 2016 Share Posted August 18, 2016 I seem to remember that the problem was of the scale that if it was negative pressure in the tank that initially the cap was held in place and hard to remove, positive pressure would present the cap to you on rotating the key along with some fuel vapour.Just a thought - From memory and from owning one, a 1400 Roadsport LE came by default with an aero cap, does it have 'Caterham' inscribed into it?, if lost a replacement cap might not (if obtained from another source) have the specific hole drilled in it.Alternatively, your car may have enough air leaks in the tank area (filler, breather, sender, cap) that once it's stopped by negative pressure (if that is indeed the problem) that a small stop, rest and restart is enough to reset things pressure wise again. Link to comment Share on other sites More sharing options...
revilla Posted August 18, 2016 Share Posted August 18, 2016 If it's positive vapour pressure you can indeed feel the cap wanting to pop out into your hand a bit. Link to comment Share on other sites More sharing options...
RyCliff Posted August 18, 2016 Author Share Posted August 18, 2016 Would I get this when just stopping at the petrol station to refuel rather than when the engine dies out? Every time I refuel as soon as I lift the latch covering the key hole I can hear a rush of air. It doesn't feel like it's trying to blow out when this happens. Fuel cap is black with caterham on it in white which I think is inscribed from memory. Seems to fit the description of an aero cap. I'll check it for any holes drilled in. Only other thing I can think of is I have to trickle fuel in as the pump clicks out, which would agree with the build up of pressure. Link to comment Share on other sites More sharing options...
The_ASH Posted August 18, 2016 Share Posted August 18, 2016 Sounds like the correct cap and that it does pass pressure, whether or not it vents enough is another question, in the original BC thread there were pics of where the hole should be in the back of the cap but as you mention it I think it did vent though the key slot.The 'clicking out' issue is normal mine does the same (and I have a plastic cap on my present car) OR allows you to completely fill the tank and then spit a load back at you as it cuts out if you fill too fast. Link to comment Share on other sites More sharing options...
SM25T Posted August 18, 2016 Share Posted August 18, 2016 The TPS reset .... master switch on. Ignition on. Don't start the engine. Link to comment Share on other sites More sharing options...
RyCliff Posted August 23, 2016 Author Share Posted August 23, 2016 Bit of an update Managed to take out the breather from the top of the tank (under the boot) and seemed clear. Tried to remove the other but this seems like a much longer task... There's a white circular item in the line which I'm supposing is the valve fitted, but beyond this the usual rubber fuel hose becomes a thin tube the thickness of an electrical cable. At the fuel tank this goes back into a regular fuel line and into the tank.Drove into work today and noticed the issue still happening but under acceleration and when going up hill, so assume it is this second breather at the front of the tank causing the problem. On a separate one, when the problem occurred I opened up the filler cap and had the anticipated air rush. However as my breather lines go back into the filler neck, should my cap not allow air through when locked in order to relieve any pressure? Sorry for the lack of basic understanding, but this is one of the reasons I got the car so am determined to fix. Thanks Link to comment Share on other sites More sharing options...
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