Mike, Interesting. My S2 also recently produced a high CO (I think it was CO not CO2 - is CO2 tested?) reading - such that it would fail an MOT. I dismantled the AFM and cleaned the tracks up (and bent the wiper arm a little so that it runs on different bits of the track), cleaned the air filter and cleaned the throttle plate. I haven't had it re-checked, but this should make a difference. The other point to note is the temperature of the engine when it is checked - if the car isn't fully (and I mean FULLY) warmed-up then it will produce an artifically high CO reading. Oli.
I once failed an MOT on CO levels - Read how I passed haha
- Thread starter zcacogp
- Start date
Evening all. Been quiet on here for a while cos of work and my broken computer (which is still currently broken) and as some of you will know I've been doing my sills/lower rear quarters.
Well I'd finally got finished and decided to put it in for an MOT today. Failed on a few bits (all simple apart from this one) which I'll sort tomorrow. I'm struggling however cos it failed on c02 level at idle. The car's currently fitted with Autothority Stage 2 chips (in it when I bought it) which I had always intended to change later as part of my upgrade path. I'm not quite ready to do this yet though (as the car's gonna be laid up next year) so looking for some help on getting the levels down.
Can anyone help ?
How much will the co2 at idle come down if I have a convenient leak in one of the vaccuum lines ? [8D]
Does anyone have any standard chips for 220bhp '88 car ?
Any other tips/tricks to get me through ? as I need the car next weekend. I fully understand that the car's not running at it's optimum with these chips, but am happy that I'm not running in danger. Just wasting some fuel for now [8|]
Hope you can help guys ?
Mike
PS - if anyone's breaking any 944 I could do with a couple of interior bits, so please fire me a PM. Ta
Well I'd finally got finished and decided to put it in for an MOT today. Failed on a few bits (all simple apart from this one) which I'll sort tomorrow. I'm struggling however cos it failed on c02 level at idle. The car's currently fitted with Autothority Stage 2 chips (in it when I bought it) which I had always intended to change later as part of my upgrade path. I'm not quite ready to do this yet though (as the car's gonna be laid up next year) so looking for some help on getting the levels down.
Can anyone help ?
How much will the co2 at idle come down if I have a convenient leak in one of the vaccuum lines ? [8D]
Does anyone have any standard chips for 220bhp '88 car ?
Any other tips/tricks to get me through ? as I need the car next weekend. I fully understand that the car's not running at it's optimum with these chips, but am happy that I'm not running in danger. Just wasting some fuel for now [8|]
Hope you can help guys ?
Mike
PS - if anyone's breaking any 944 I could do with a couple of interior bits, so please fire me a PM. Ta
DavidL
Active member
Further to Mike's comment about making sure the engine is up to temperature, also make sure they aren't testing it with the fans running as this really messes your emissions up! The MOT tester should know this but mine didn't and promptly failed my Caterham as the fan is hard wired on currently. Pulled the plug and hey presto a normal emissions sheet.
My old 220 turbo also failed the mot with its Autothority chips fitted so I took them out and put std in and it still failed. I swapped out the big fuel reg and changed AFM at the same time and all was well. So sorry its a rubbish answer but I think it was the fuel reg not the AFM.
Diver944
Active member
Most aftermarket chips don't alter anything down in the idle range, it's normally just in the full throttle, maximum boost area [8D] I would also suspect the Fuel Pressure Regulator. If you do have an aftermarket 3 bar version fitted then try the original 2.5 bar just for the MOT
appletonn
New member
Hi Mike, unlucky there mate. Mine passed both times whilst fitted with the 3bar fuel regulator, so doubt it is that. Oil's suggestion re the AFM would make sense plus ensure the airfilter is clean (or temporarily missing [
]). The other thing is that it has not been used properly for quite a while, so perhaps an 'Italian tune-up' is in order?! There are loads of stories of city cars failing MOTs as they never get a good run to clear out the tubes. Good luck
]). The other thing is that it has not been used properly for quite a while, so perhaps an 'Italian tune-up' is in order?! There are loads of stories of city cars failing MOTs as they never get a good run to clear out the tubes. Good luck
NeilW
New member
Mike, +1 on the no fans comment above. My old S failed with fans running and passed with them disabled. It turned out that a bad connection at the battery was causing a poor spark, made worse with the additional electrical load. My battery terminals looked ok when checked visually, but weren't performing under load. I replaced the negative completely, easy as it's a short grounding cable. The positive, I cut back the cable by an inch or so and re-terminated with a new end. Good Luck.
OK guys, all good thoughts there, many thanks. Engine was fully up to temp, though I can't remember if the fns were running or not ? It's on the original FPR, so is it worth upgrading to the 3bar one I'd been planning for some time ? It may be bigger but at least it'd be brand new. Don't really wanna buy a new standard one to then change it for an uprated one in the future. Will strip and clean the AFM today and see how it all looks. Interesting you say they don't alter fuelling at idle Paul - I didn't know that. There is hope I can get it through then without splashing for new MaxHP chips which I'm not ready for yet. Will keep you posted on results - but if anyone has any other info, please feel free to post up. Thanks guys [] Mike
] MikeIt's just dawned on me that I have a slight problem which may be related and help people to diagnose ? When starting the car from stone cold, the revs sit quite low and the car runs a little rough. If the revs are raised a few hundred rpm's or more for around 8-10 seconds, the rpm will increase a few hundred on it's own and the car will then idle normally. It all runs fine from then on, this is only an issue when the car is started from cold. I'm assuming this is a sensor related issue ? could this be related to my high co2 @ idle perhaps ? Thanks in advance, Mike
Vaccum line leaks may have an effect, A good thrashing will probably help, redline it in the lower gears when warm - didn't that fix Will's a few months back? what was the CO figure? Also if you open the throttle butterfly by hand do you hear a click just after its come off the stop? (engine will need to be off) How old are the plugs? Tony
Plugs are only 200 mls old if that. Leads are all god. Will try the click when opening the throttle butterfly - what does that indicate ? is it a break in the track @ idle position ? I'd given it a bit of a pasting on the way up there, so I was fairly happy it was running normal and was up to temp etc. Wouldn't a vacuum leak lean the mixture off ? Mike
There is a microswitch that triggers when idling, it releases when you move the butterfly off the stop. The potentiometer/switch assembly has some adjustment which means it is not always set correctly and sometimes strange things occur at idle if its not set right. Also there is an Idle mixture screw (hex iirc) on the AFM (its basically a bypass and may be under a cover) and the idle speed adjustment screw on top of the throttle butterfly. The mixture and idle speed should be adjusted with the ISV disabled. Vacuum leaks can do strange things but yes they should lean it but have seen some strange behaviour. On the later cars there was also an emissions pipe that came up from the exhaust manifold at the rear of the engine - when the cap on mine split it failed massively on CO dont understand that either but replacing it fixed it! A small exhaust leak might cause the same but then that should have been picked up on the MOT. Tony
OK, AFM stripped, cleaned and arm adjusted now. There were worn tracks but problem still not fixed. Microswitch seems to be working ok Paul-can hear it clicking as you move the flap off the stop. Can someone please tell me the correct resistance of the engine temp. sensor at cold ? I've tested mine and it's around 3.1Kohm but without a reference point I'm unsure this is correct ? REALLY appreciate someone checking there's so I have a known good value. Dizzy cap and rotor arm on order for this afternoon as they were found to be in poor condition (can't believe I forgot to check them when servicing it earlier in the year ! [8|]) Cheers, Mike
Mike, I'd love to help, but my car is currently being repaired! However I will ahppily measure it when it comes back (with the cabveat that mine has similar symptoms to yours - high CO) and let you know. If anyone else with a known-good car could measure theirs as well and post the value here that would be great. Oli.
Oli, appreciate the offer bud [] hope you get sorted - what you havin done ? Paul - legend, thanks. Checked in clarkes but it only gave values when the temp was starting to rise. Yes, happy that it's working fine. Just gotta wait and see what difference the rotor arm and dizzy cap make now........... Thanks guys, Mike
] hope you get sorted - what you havin done ? Paul - legend, thanks. Checked in clarkes but it only gave values when the temp was starting to rise. Yes, happy that it's working fine. Just gotta wait and see what difference the rotor arm and dizzy cap make now........... Thanks guys, MikeNew rear bumper after a friendly cabbie decided he'd rather use my car than his brakes to stop. Dizzy cap and rotor arm could be a major step forwards. High CO means there is unburned fuel in the exhaust. This can be as a result of the fuel not being properly ignited, because of a poor spark. Old dizzy cap and rotor arm can be the cause of a poor spark. (Another cause of unburned fuel in the exhaust is that the engine is running rich, as a result of the AFM not reading the air flow correctly and thus putting too much fuel in. This is why cleaning the AFM tracks is a good idea. OR it can be running rich because the ECU thinks the engine is still cold, and hence it's a good idea to test the engine temperature sensor - as you did. Please don't read this paragraph as patronising - it's all stuff I am sure you already know. However when it was explained like this to me then I found it helpful, and other reading this may be the same. [ORIGINAL: mike220 Oli, appreciate the offer bud [
]) Oli.Not at all Oli, all help welcomed. Tracks cleaned and temp sensor checked. I worked my way through it logically which is how I ended up checking the dizzy/rotor etc. Was surprised at how bad they were, so here's hoping we see a marked improvement like you say. Parts should be here within the next hour hopefully, so time will tell . . . . .. . . . . . . . . i'll keep you posted. Hope you get the bumper sorted soon with no hassle. Mike
New dizzy cap and rotor arm fitted, off to MOT testing centre tomorrow to see if it's made any difference ? Will post up results. Tony, you mention the microswitch on the throttle butterfly/throttle body. I'm now not 100% sure I can hear this. Any pointers as to where/how to check it ? Or setting the throttle stop etc. up correctly ? Cheers, Mike
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