Menu toggle

CO2 Emissions on 944

IIRC the ICV will buzz when the ignition is first switched on without the engine...best to get someone else to turn the key while you listen. Put a large screwdriver handle to your ear while the blade is resting on the ICV, you should be able to feel as well as hear it switch on. I can't recall but think the ICV only gives a short buzz when first switched on
 
The ICV or very close matches were used on lots of cars of the era, so can be replaced much cheaper than the AFM
 
Definitely doesn't buzz with ignition on and engine not running...just the one clonk (ie the solenoid is activated just once) as ignition made. The 944S (and I think the 944S2 just has a 2 pin ICV, is the buzzing thing only happens on the 3 pin ICV on pre 1988? the ICV valve does something because disconnecting the connector it stalls so possibly it may be this aftermarket Chip in the ECU causing fuelling issues with cold starting


I'm yet to fit a standard Eprom,when I have manage to source it I hope refitting a standard Eprom it resolves it!! but if it still hunts on cold starting I'm going to spend time checking the AFM air temperature sensor at source (impedance/voltage) at the AFM and cabling back to ECU along with the engine temperature and TPS switch, so back to basics and elimination now, or a wrongly adjusted AFM ?

John
 
Hi John

Other than a possible leak your ICV is probably working fine...I'm not familiar with the layout on the N/A's but if like the turbo's the area under the inlet manifold is very hostile and plastics and hoses failing due to heat is common. While trying to source an Eprom perhaps in the meantime remove the inlet manifold and check everything under it for leaks. Replace the manifold gaskets while at it. Despite what some say these cars are very reliable and often keep running when parts fail that would ground lesser marques.

My son recently replaced my inlet manifold gaskets after finding one had failed whilst searching for an issue, the car was running fine other than a small flat spot low in the rev range which has now gone.


Pete
 
Hi Pete Unless the ICV doesn't something clever on cold starts with it modulate which i doubt it does as it only required to be open bypassing the throttle body with a closed barn door and richer mixture until warm stays open on this ICV path for a couple of min's.
within reason I'm pretty confident the manifold, vacuum hose and the larger rubber hoses around the venturi are solid (oddly here I'm stuffed as these larger "Y rubber hoses" are now NLA from Porsche I've tried globally too and aren't availble which is a P*sser) but within reason I think everything leak free but I hope I'm right....!!!!
I've used so much quickstart around that area I could have blown the car up with the quantity used I started floating around in the garage too:ROFLMAO: and it doesn't react to any leaks sucking it in and rev'ng up.
I've invested in a PC based oscilloscope and just manage getting it working on a Macbook.
I've be removing the afm cover again to poke around there and try and work out and get an idea what happening and if it getting back to the ECU pcb here even though is got this chipped Eprom in there, see what the ICV actually doing too, again there info out there the power IC (darlington driver stage transistors fail on the pcb) again this may be another mis information but at least I have a scope to poke arond with rather that swapping out or just relying on a multimeter...oh Joy!
 
try this for some help
http://pdlibrary.co.uk/Manuals.php then the L-Jetronic tech instructions

has some values in it which might or might not help,

and looking around its not that horrid to buy a new AFM, I can find brand new ones for £220, with second hand ones on bay of fleas and other places wanting far more




 
Cheers Martin and Pete, checking some basics now may possibly may invest in a new AFM to future proof the car, But I hope someone comes up trumps with a ECU Eprom and I can eliminate that
one
John
 
AFM so the black cover is off again, for investigations so scoped the voltage off the resistive strip ie barn door position and reasonable clean on arc of travel slight noise pick on track at idle position as expected would overtime would wear quickest here scrubbing away on tickover.
So perhaps problem1)
So have noticed the wiper pickup "no throttle" which relates to start of track isn’t at the start of the track (starts at 650ohms not 0) this may be normal but oddly sweeping to maximum it falls off the PCB completely surely it can't be right.... so lve looked at a couple of photo on a few 944 variants and what l can see should start at the start of track ie 0’ish ohms. So FFS if this is the case I seen the spring tension which l marked has been moved at least 25degrees too from when it went in to the garage. I’ve checked the Air Sensor whilst the lid was off and measure 2k7 ohms at 18o temperature and what Clarks garage ball park range. For those that may have been in this "little wonder land AFM" and magic world of adjustment have you noticed where the wiper starts and ends and should it fall of the end of the track completely it may be normal as the barn door perhaps never opens that far at 7000revs?
I'm at this stage not randomly tweaking (yet) because l don’t have that expertise with this "black box of variables" and with no exhaust analyser either let alone been its been got at before before me and again with the recent garage visit as well ...Oh Joy
Does anyone out there know and expert to get it back in Spec?
will supply photos showing wiper start and maximum travel
 
I have increased the tension on the afm spring in the past, I suspected it was weaker after many years of working and it improved my air fuel ratios, not sure this is the issue hear.

In this case I would bypass the ISV with a suitably sized piece of tube I bypassed the one on my turbo coupe as it leaked, without it Idle is a little low on cold starts and slightly high on hot idle, if it cures the issue you will know. (there is a way to disable it electrically - however if it has loose parts this might not rule it out)

My Cab occasionally (when it hasn't been used for a while) revs itself several hundred RPM on a cold start. if I unplug the AFM it continues to run and with a much smoother tick over - plugging it back in usually is enough for it to be fine, I think the contacts develop a small amount of corrosion. However this may be a quick check you can do - unplug the afm while it is running and see if it 'calms down'.

Worth checking the Throttle position switch 'clicks' as it lifts as throttle blade is opened (engine off) there is a microswitch in there to tell the ecu its closed in the idle position. Wont guarantee its good but it can be set so it isn't operating so you can rule that out.

Looking for air leaks is worthwhile and may improve things - hopefully easier than on a turbo!

Tony
 
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 twat 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 ?

 
With your help have found a few but mainly overview and system parts hopefully will find a idiots setup guide, as you know exhausted anything Porsche related continuing with options on VW and BMW threads/Info
 
One of the connectors on the AFM is sensitivity I think, I had problems with this over the years making the car run rich. A scoot of DeOxit onto the connector and loom plug every now and then cured the issue. Again not sure if this relates to any of your issues.

Stuart
 
Not sure if they still do them - but as an FYI, I got a "remanufactured" AFM form Frazerpart for my 944 S2.

Ian
 
Wow,

it was 3-4 years ago but I paid £400 tops.

I should add that changing it didnt fix the problem! I also tested the ICV, rewired a dodgy hall sensor, changed the TPS and the engine Temp sensor with no luck. In the end as part of a clutch replacment I had the flywheel sensor chnaged and it ran perfectly with low emissions after that :rolleyes:
 
Hi Ian
Yes I treading in you footsteps, realistically although those reading this now and are trouble free.. but...I'll put money on this so 5 to 10 years from now like minded owners of 944's 968, 911 will be placed in this running nightmare issue searching for a fix everywhere, so ALL take note in the future with end of life with surviving left AFM's so probably with knackered unusable tracks now to us searching for scrap units with a view to make usable and with those twats adjusting them making them useless in the mix, then add this knowing that "EXPERT" (sadly that generation will disappear completely by then) to set the bloody thing up correctly to work......So the solution facing us does the complete upgrade to MAF and new ECU the only way out in the future, I been chewing over this there a easier way out replacing the "Wiper and resistive track" and replace with a contactless sensor providing the positional volts directly to the existing ECU. So is that man in the shed out there to knock one up, these unit could be desirable as they're used in all 944's BMW E30 and VW using this ridiculous method giving positional information to the ECU for Map Lockup values??? Or am I mad suggesting this ?? pinch me and I'll wake up or is there a miracle possible ?
 
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
 
You must log in or register to reply here.

Posts made and opinions expressed are those of the individual forum members

Use of the Forum is subject to the Terms and Conditions

Disclaimer

The opinions expressed on this site are not necessarily those of the Club, who shall have no liability in respect of them or the accuracy of the content. The Club assumes no responsibility for any effects arising from errors or omissions.

Porsche Club Great Britain gives no warranties, guarantees or assurances and makes no representations or recommendations regarding any goods or services advertised on this site. It is the responsibility of visitors to satisfy themselves that goods and/or services supplied by any advertiser are bona fide and in no instance can the Porsche Club Great Britain be held responsible.

When responding to advertisements please ensure that you satisfy yourself of any applicable call charges on numbers not prefixed by usual "landline" STD Codes. Information can be obtained from the operator or the white pages. Before giving out ANY information regarding cars, or any other items for sale, please satisfy yourself that any potential purchaser is bona fide.

Directors of the Board of Porsche Club GB, Club Office Staff, Register Secretaries and Regional Organisers are often requested by Club members to provide information on matters connected with their cars and other matters referred to in the Club Rules. Such information, advice and assistance provided by such persons is given in good faith and is based on the personal experience and knowledge of the individual concerned.

Neither Porsche Club GB, nor any of the aforementioned, shall be under any liability in respect of any such information, advice or assistance given to members. Members are advised to consult qualified specialists for information, advice and assistance on matters connected with their cars at all times.

Porsche
Lockton
Pirelli
Officially approved
Oracle Finance
WEX Esso
Collecting Cars
Archant Dialogue
Back
Top