bit of a strange one this. last year i fitted my cat a week before my mot. all ran fine, no real difference apart from being quieter! but after a few days the car would not rev over 5500 rpm. started checking all the sensors etc… wheels speed, lambda, etc etc… all seem ok and confirmed this at a lotus dealer with their little plug in thing. i changed back to the cat replacement pipe and it did not sort itself out for a few days and one day it started working fine again. i thought it must have been a sensor i had wiggled the night before, and all is well.
the car runs perfectly for the following year.
so this years mot the same thing happens! fitted the cat, the car runs fine for a few days, then starts this misfiring rev limiter 5500rpm thing and i want to find out why.
my car seems not to like having a cat fitted!
does anyone have any ideas?
by the way the car is a stock everthing with the factory 190 kit. airbox, supersport exhaust and 190 ecu.
Almost always seems to end up being the ECU wheel-speed sensor and/or its associated cabling that goes wrong due to being disturbed/getting hot/abrading on the bulkhead/cosmic rays/magic pixies . Maybew just replace the lot. Good luck.
i think it could be the pixies. the bad ones who are not supporting greenpeace. as this only happens when the cat is fitted and starts randomely a few days later after fitting the cat and stops randomly days later when the cat is removed.
i shall stay up late tonight and try to catch the little sods.
Mike, my guess would be that the cars Stock ECU has self learning capabilities and has learn’t to run with fueling, back pressures etc with the Cat off which is most of the year. Once the Cat goes back on it takes a little while for the ECU to detect a different running setup it then sees this as a fault and reverts to it’s limp mode map giving you a get you home 5,500 rev limit. I think the way round this would be to :
a. Reset the ECU once the cat is re fitted
b. Put up with it for the yearly MOT.
hi chris, that theory fits quite nicely. although after removing the cat and doing the ecu reset. (as long as i did it correctly. ignition on, 5x full gas pedal depression, and then off.) it still took a seemingly random ammount of time to fix itself again!
I’m still plagued with a misfire in the 4,500/ 5,000 rev range when under load and that’s without the cat. It all started after fitting new exhaust with cat replacement pipe. Had new plug leads fitted but that’s not done the trick. Checked wheel speedsensor. Once or twice it’s seemed to clear up but then returned. I have not tried the ECU re-set. Is it as you described?Ignition on, 5x throttle depressions etc?
That might well be the DIY version but i am sure that that doesn’t totally reset it CLEAN ready to start again. From my experiences with ECU’s they need time free from any power source and even this can leave some CRAP in the brain …
I always thought Lotus recommended that a cat replacement pipe is fitted as a part of the 190 ps set up. Is it possible that a reprogrammed ECU requires a CRP and that a standard cat may therefore trigger the safe mode? Can ECU detect change in back pressure? I do, however, have a 190 car, which is equally happy with/without a cat…
I always thought Lotus recommended that a cat replacement pipe is fitted as a part of the 190 ps set up. Is it possible that a reprogrammed ECU requires a CRP and that a standard cat may therefore trigger the safe mode? Can ECU detect change in back pressure? I do, however, have a 190 car, which is equally happy with/without a cat…
I regularly swap mime as well and have been doing so for years. Although the car clearly runs a bit crisper with the CRP it runs perfectly well with the cat fited as well. There must be a sensor out somewhere…
It’s quite possible that the Cat is Knackered, they break up and colapse inside this could cause irratic backpresure which is some how throwing it into limp mode…
If possible try another Cat on your car from someone who’s car runs fine with it attached, atleast you will iliminate this from the equation…
I hope all is well for the Ring, spent nearly 40 hours now on the Liner as the Exige seems like a definite No Go…Gutted (need to find a bucket seat and harness)
if all you are needing is a seat and harness then i am sure they cannot be too hard to find. i mean, you did have seats in the old red baron didnt you?
still, looking forward for a trip down turbo tastic memory lane in the liner. whoooshh pop.
good idea with the cat. maybe should try and borrow one.
i still havent had chance to get it warm enought to give it a bit to see if the ecu is playing ball again. i hope it is once again running up to full rpms.
otherwise i will be doing even slower laps than usual at the ring.
a simple “running in - please pass” sign will surfice for the weekend i think.
I am pretty sure you will find that the cat has started to break up inside and is therefore restricting the flow, it will only get worse and eventually not allow the car to rev at all !!