CO2 Emissions on 944

jellytott · Oct 30, 2021

Waylander said:
Ah, not 968’s we have a proper MAF, but we also have an issue
our particular MAF was only used on the 968 and the RS2
it is available as a recon unit £1467.00 exchange

Yes thats even more restrictive than the 944 AFM's even more costly too as you know my thoughts of possibly investigating in a adaption to the 944's AFM weakness with the carbon track and wiper sensor its just thoughts and all chat it another thing to actually doing it and if it actually works at sensible price per unit too.

scam75 · Nov 1, 2021

If you are lucky enough to pick up a SciVision MAF kit, would need to be 2nd hand, you can bin the AFM. The SciVision, which I have, is a half way house that ditches the barn door AFM in favour of a hot film MAF, a reliable Bosch HFM-5 unit. And the supplied wiring harness adapts the MAF signal so your ECU understands it. It's obviously not a true MAF, but my car breathes and runs better with no AFM issues since I installed one. IIRC they were about £800 new, I paid about £400 a good few years ago. You can purchase brand new HFM-5's for under £100 these days so wouldn't break the bank. I seem to recall the same kit did all 944 models. So even if you could find a SciVision harness 2nd hand you can purchase a new HFM-5 to go with it. IIRC you also need a basic adapter to connect it to the airbox but anyone could make that up.

Air Mass Sensor 0281002447 Bosch Flow Meter 2816427000 HFM5 Quality Guaranteed | eBay

951 SciVision Plug & Play MAF Kit - Pelican Parts Forums

Stuart

944Turbo · Nov 8, 2021

jellytott said:
Hi Tony
Unplugging the ICV it stalls, pretty happy there's no leaks, TPS checked too as said hall sensor and ref replaced, the other unknown is the Chipped Eprom in the ECU I'm in the process of sourcing.

Looking for someone that could re-calibrate the AFM I definitely spotted (I think and pretty certain) that's adjusted wrong and I know clouding my AFM is the spring tension been moved 20 plus degrees too! I'm don't want to randomly tweak things Really as there's plenty of warning adjusting the mechanicals in it but what happens if some **** has!
Checking/adjustment of Spring tension unknow. I would like to know how this is adjusted, suggestions was a plumb weight of xx Grams will cause the barn door to open/drop to a yy Distance measured from the mouth of the AFM input face, with this right and the whole selection of sensors no leaks etc, the AFM potentiometer wiper pickup starting from the right place ( here I feel mine isn't) as said with no leaks, sensors, ICV, TPS, wiring and ECU all working as they should and if so the "slow idle adjust" should set the tickover correct and CO2 and NOX in spec too......Well I hope so thats my dream.....So there surely be a Guru in a shed of the older generation that just knows what and how to set it up ?

If it stalls when you unplug the ICV then it is probably doing something. What about if you unplug the AFM while it is ticking over? (and if the ICV in your first line should of been AFM) if it still stalls can you detect the microswitch in the throttle position sensor clicking as you lift off idle?

The idle speed adjustment screw on top (or maybe to side on na) of the throttle body I believe has an o ring on it I would check this for damage (turn it in counting the turns - then back it out to remove - then when you put it back go all the way in and count turns back out to original position). I think there is a throttle stop adjustment on the cable this should be used to set the throttle blade position closed not to adjust the idle speed. The idle speed adjustment allows air to bleed past the throttle body

On the 8v (not sure on the 16 but I suspect the same) beside the AFM there is an idle mixture screw, (this just lets are bleed around the the airflow meter blade) check that isn't loose - it has a small round cover over it from the factory, but most are removed. I recall many years ago someone saying theirs had worked loose and was rattling in the hole - again use the turns in /out I think it is a 2 or 3mm allen key - but its a long time (20 years + !) since I played with one.
Its not your problem but on my coupe when it was standard I had a high Co reading for the mot - on the 90 turbos there is a port in the exhaust ( a long tube that comes up form the exhaust manifold pre-cat) for checking the emissions, that was leaking on mine giving high CO readings at the tailpipe - it couldn't be adjusted out with the idle mixture adjustment screw on the air flow meter, though it could be made worse!

Playing with the airflow meter spring changes the mixture through the rev range (for the duration of its its travel (around 1000 - 4200 rpm before it is fully open and the car switches to look up tables in the ecu)), at idle I think it is almost closed though a weak spring would allow it to be more open and you may run richer - tighter spring you should run leaner. Not sure on the actual resistance values.

Other than the hunting idle does it run ok?

Tony