Ford1.6 Sigma running very rich after cap popped off. Ideas?
Discussion
Caterham Roadsport was running fine until a small black cap popped off just before Graham hill bend @ Brands. When the cap was off the engine would rev up to the limiter. This is the cap: It the same as the one below the Caterham air filter.
We replaced the cap and fixed it place with a jubilee (it just sat on before) but now she runs very very rich. I checked and replaced the plugs and they are covered in soot
I'm totally stumped and know nothing about this engine or what the cap does but after that it's all gone wrong.
Can anyone give me a helping hand with some advice/knowledge?
We replaced the cap and fixed it place with a jubilee (it just sat on before) but now she runs very very rich. I checked and replaced the plugs and they are covered in soot
I'm totally stumped and know nothing about this engine or what the cap does but after that it's all gone wrong.
Can anyone give me a helping hand with some advice/knowledge?
I'm intrigued as to how you could know a small cap had popped off in a concealed area under a closed bonnet at a specific place on a racetrack without some very extraordinary X-ray vision. This leads me Watson to the deduction that the circumstances of the case may actually be more like the following...
You were driving round when the engine stopped running properly. You got back to the pits and opened the bonnet and then spotted a little cap lodged somewhere and thought "Aha, where does that fit?" You raked round until you found a convenient stub that looked handy but the cap didn't quite fit it properly so you added a jubilee clip.
Am I anywhere close?
You were driving round when the engine stopped running properly. You got back to the pits and opened the bonnet and then spotted a little cap lodged somewhere and thought "Aha, where does that fit?" You raked round until you found a convenient stub that looked handy but the cap didn't quite fit it properly so you added a jubilee clip.
Am I anywhere close?
Edited by Mignon on Wednesday 30th November 07:59
Thanks for the replies.
Nope not even close. The car went WOT on track causing my wife to spin and wouldn't stop no matter what we checked. An eagle eyed Caterham owner spotted the cap. It's nearly impossible to spot, if he didn't see it would still be WOT. We put it back on and it revs normally but rich.
The previous owner has since informed me this used to form part of a breather setup but the upgrade made the exit redundant hence the cap.
Nope not even close. The car went WOT on track causing my wife to spin and wouldn't stop no matter what we checked. An eagle eyed Caterham owner spotted the cap. It's nearly impossible to spot, if he didn't see it would still be WOT. We put it back on and it revs normally but rich.
The previous owner has since informed me this used to form part of a breather setup but the upgrade made the exit redundant hence the cap.
Having a sealing cap fall off the intake manifold would stop the engine returning to idle and would usually make it run lean at part throttle. If the cap is not a good fit on the spigot you think it was supposed to seal then I would question your assumption that is where it came from, because if this has been loose the whole time the air leak in the intake manifold ought to have been very obvious.
I don't see how that air leak would make the engine run rich once it was fixed, unless the engine had been miss-tuned to allow for the air leak - which would be an extraordinary thing to do. That would make me wonder whether you had some other problem, such as a vacuum reference hose to the fuel pressure regulator come adrift or knocked loose while you were poking around looking for the air leak. That would also make me wonder whether the disconnected spigot was actually supposed to be connected to something. My last thought is whether the problem was triggered by any sort of backfire which might have damaged a sensor at the same time - if a backfire damaged an air flow sensor or MAP sensor this might be screwing up your fueling. (If you're using alpha/N that's unlikely to be the problem.)
I don't see how that air leak would make the engine run rich once it was fixed, unless the engine had been miss-tuned to allow for the air leak - which would be an extraordinary thing to do. That would make me wonder whether you had some other problem, such as a vacuum reference hose to the fuel pressure regulator come adrift or knocked loose while you were poking around looking for the air leak. That would also make me wonder whether the disconnected spigot was actually supposed to be connected to something. My last thought is whether the problem was triggered by any sort of backfire which might have damaged a sensor at the same time - if a backfire damaged an air flow sensor or MAP sensor this might be screwing up your fueling. (If you're using alpha/N that's unlikely to be the problem.)
GreenV8S said:
Having a sealing cap fall off the intake manifold would stop the engine returning to idle and would usually make it run lean at part throttle. If the cap is not a good fit on the spigot you think it was supposed to seal then I would question your assumption that is where it came from, because if this has been loose the whole time the air leak in the intake manifold ought to have been very obvious.
I don't see how that air leak would make the engine run rich once it was fixed, unless the engine had been miss-tuned to allow for the air leak - which would be an extraordinary thing to do. That would make me wonder whether you had some other problem, such as a vacuum reference hose to the fuel pressure regulator come adrift or knocked loose while you were poking around looking for the air leak. That would also make me wonder whether the disconnected spigot was actually supposed to be connected to something. My last thought is whether the problem was triggered by any sort of backfire which might have damaged a sensor at the same time - if a backfire damaged an air flow sensor or MAP sensor this might be screwing up your fueling. (If you're using alpha/N that's unlikely to be the problem.)
Factory ECU.I don't see how that air leak would make the engine run rich once it was fixed, unless the engine had been miss-tuned to allow for the air leak - which would be an extraordinary thing to do. That would make me wonder whether you had some other problem, such as a vacuum reference hose to the fuel pressure regulator come adrift or knocked loose while you were poking around looking for the air leak. That would also make me wonder whether the disconnected spigot was actually supposed to be connected to something. My last thought is whether the problem was triggered by any sort of backfire which might have damaged a sensor at the same time - if a backfire damaged an air flow sensor or MAP sensor this might be screwing up your fueling. (If you're using alpha/N that's unlikely to be the problem.)
Well the cap was a press fit but was working fine before it popped off(reason unknown for it popping off) Now it's secured and idling correctly. Just rich.
I agree there could be another issue. I have checked all hoses and tightened but there was nothing obvious. I wasn't driving at the time so i'm not sure on the backfire but i certainly think something happened to case the chain of events perhaps it was a backfire/sensor issue. I'll clean and check connections and try again.
Sounds silly but have you disconnected the battery overnight and tried again ?
Depending on the setup, an air leak of that size would have the ECU upping the fueling as it would be running lean according to the O2 sensors.
Running lean is bad so presumably ECU's very quickly adjust for it but perhaps take a while to correct rich running.
Someone with a bit more technical mapping knowledge might be able to shed some light.
Depending on the setup, an air leak of that size would have the ECU upping the fueling as it would be running lean according to the O2 sensors.
Running lean is bad so presumably ECU's very quickly adjust for it but perhaps take a while to correct rich running.
Someone with a bit more technical mapping knowledge might be able to shed some light.
If its running a factory OE ecu then get it scanned you can then monitor the short term fuel trim and 02 sensor health/voltages/activity it may even show a failed coolant sensor/air mass mater etc thats causing your problem otherwise IMO your just pissing in the wind, but please use someone that can interpret the info otherwise your no better off 
scanning tools are aids not cures
scanning tools are aids not cures GreenV8S said:
Having a sealing cap fall off the intake manifold would stop the engine returning to idle and would usually make it run lean at part throttle.
If the engine uses MAP for load sensing, an inlet manifold air leak is the equivalent of opening the throttle so it should not run lean.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff