Menu toggle

My bad day with emissions

A

audicdl

New member
Hello all, today I took my car for an emissions test just to make sure I'd turned the mixture screw down the right amount a couple of months ago after I'd had it MOT'd and it was 2.8%CO.
Imagine my surprise when the freshly calibrated machine went off the scale which meant that the car is putting out above 9.9%. This was made even worse when I discovered that the mixture wouldn't adjust at all.The screw turns but has no effect on the readings.
Has anyone else had these problems?
I'm suspecting that the airflow meter has gone faulty but would like a bit of confirmation.
If it is this part does anyone have any recomendations where to buy one from relatively cheaply please?
Thanks
Chris
 
Update, I've just been fiddling in the garage and it would appear that it's the air intake temp. sender thats U.S as there's no resistance from it. It's an integral part of the airflow meter. Does anyone know if you can take this unit apart and fix the item?
Thanks
Chris
 
I don't, but the good news is that you can easily find a second hand 964 AFM for not a huge amount of money if you need to replace it - its the same part but newer (obviously) and usually covered a lot less miles.
 
Thanks for that I'll bear it in mind. I've opened the unit up but it definitely isn't a diy repair proposition.
Chris
 
There's one on ebay, not sure if it's any help.

Type in "Porsche 911 air flow meter" in the ebay search engine.

It's at £26 at the moment.
 
I don't think it is a good idea to buy a AFM second hand unless you can trust who you bought it from. It may be worn out.

I certainly wouldn't get one from Douglas Valley Breakers [:mad:]
 
I did toy with getting the second hand one but decided that it probably was false economy as I plan to keep the car for a while. Mrs Lindley decided that I was on a spending ban for anything other than essentials!! So I wasn't even allowed to research that Promax item[:(]. So in the end I bought a reconditioned airflow meter from Andrew Page motor factors for £200 including VAT. Bosch seem to have stopped selling brand new ones. Whilst the old one was off I found some seriously cracked and perished oil breather pipes as well so that was an extra £60. It all seems to be running well but I'm getting the emissions checked on Thursday so fingers crossed.I'm sure that all is well though.
Chris
 
Can the Lambda play a part in this in failing CO correction? My '87 has developed a very rich mixture at idle (although it seems fine at the cruise - still returning good economy). I replaced the idle air bleed bypass valve and fitted a Bosch recon AFM (using the somewhat expensive 'replace things one by one until it works' approach). My nose mounted CO meter still indicates that the exhaust is smelling very rich on idle. MoT is due soon and so I'm wondering what to look at next - the Lambda sensor seems like a good candidate? Do they fail much?

The car performs very well otherwise, with only an occasional tendency to backpop on blipping the throttle when changing down, so I'm guessing the ECU is OK.
 
Probably not the problem here, but my AFM has 'failed' twice according to the garages doing the annual service. Both of which have tried to sell me a replacement.

Upon return of the 3.2 I placed the air filter in the correct orientation (has the word TOP printed on it) and the CO levels were back to normal.

Needless to say the service was not carried out at these Porsche specialists again.

DBA
3.2 Carrera Cab in Cassis
 
Tail heavy, after doing a bit of reading about the mixture, apparently if the cylinder head temp sensor fails, the ecu thinks the engines cold and makes the mixture too rich. You then can't adjust it on the afm. You can do a check with an ohmeter to see what readings the sensor is giving. It's allegedly quite a common fault.
Chris.
 
audicdl, thanks, that could be just the tip I'm looking for. Of course it makes perfect sense when it's written down like that! I'll source and fit a new sensor and report back. Thanks also, by the way, for starting the thread.
 
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