rite then peeps! me again with more probs ! haha!
BAD FUEL!!!
i have changed the Lambda sensor… the FRONT one, and i have JUST found one on the cat… i thought there was only one! lol
so its either the 2nd lambda sensor or the Water Temp…
depending on price, ill change both, but wot is the best way to check it? and identify… tryed pluggin in a engine code reader thing, but was having none of it ! 
any ideas peeps?!
The sensor you’ve found in your cat is not a lambda sensor,but an overheat warning. A lot of these fail at some time, switching on a ‘HEAT’ light on the dash. In most cases all you need to do is to snip the wires or disconnect the sensor.
As far as getting info from the ECU have a look here:
http://www.mx5oc.co.uk/forum/forums/t/204.aspx
Good Luck
why thank you very much!!! 
will have a looksy!
thanks!
iv still got problems…
iv done the LED thing… and has brought up NO fault codes!!! wot? ! ! ! !
if it were to have an MOT, it WILL fail on it, as my mate tested it for me 2day! its Rich as FOOOK, and i dont mean rich… i mean EFFIN RICH… really bad like.
checked the air filter, seems alrite (makin sure no blocks)
its got a new Lambda sensor,
but as there is no codes, wot is next, im gonna attemt the Co2 thingy on the AFM… maybe sumone has potched b4 i had it ? thats all i can think of tho?!
Hello chap, would you mind moderating your language slightly ‘foook’ isn’t a very polite word.
What do you mean by Co2 on the AFM?
Also it’s only ever going to be one of two (possibly 4 but unlikely) things, either your timing is massively out (does the car feel sluggish to drive? and then suddenly pick up?) or it’s your lambda sensor.
please disconnect your battery and hit the brake pedal for 10 seconds, then reconnect the battery and see if that solves it
does it misfire at all? Is it definitely firing on all 4 cylinders?
hopefully we can help you, but we need more info!
on the AFM, there is usually a Co2 adjuster screw… it fiddles with the mixture. most AFM’s do…
i dont think the timing is out, but i suppose i can check it… dont feel sluggish, seems to pull from the 1k upwards an onwards… the lambda has been replaced, about a month ago…
i done the battery thing when i changed the Lambda…
it dont miss fire atall… and is deffo 4 cylinders…
like i say, it runs like clockwork, and like a dream… but DAM its expencive to run! haha! an the tests i had carried out the other day show how far the actual fueling is… VERY bad, think it was like 2.300 and its supposed to be 0.900 for the year… thats Co2 by the way! 
Idiot (me not you) the answer is staring me in the face
Water Temp sender. There are two on the engine, one for the gauge, and one for the ECU, if the ECU thinks the engine isn’t warm, it never drops out of cold start mode. I’d change that…
Have you tried one of those magnetic fuel savers? http://www.ecomagnets.com/motoflow.htm
this is the thing… thats wot i thought it was … BUT… there was no code popping up on the reader??? Code 9 IIRC?
well i know they aint that much to replace, so i think ill have to do it !
my lecture in Uni 2day suggested it was the Co2 screw in the AFM too, as it was showing no faults… soooo…
NTC2 (water temp ) it is. THEN try the screw on the Gas Anaaaalizerrrrr!
thanks chaps. shall let u know how i get on !
The 5’s ECU isn’t exactly high tech…a sensor has to be ‘obviously’ out of parameters usually, so a failed sensor doesn’t ALWAYS trigger a fault code.
Seem to remember that one ebay bodge for extra power was actually a resistor shunt over a sensor to fool the car into running rich might be worth looking for something bodged on the car like that too. Water temp or air temp, can’t remember which sensor was shunted and if it was at connector or directly across though
both good points…
taken in! thanks !