Rich Idling

[robwright]

Evening all after much battling and removing of Turbo plumbing I managed to change the DME coolant sensor today. It did not however cure my problem of rich idling. I am not disappointed that I did change it though. So I have checked the throttle position switch and that is working fine and the resistance readings of the new coolant sensor check out just fine. So what else could be causing it? There is no mixture adjustment so what's left? I can only think of the AFM but that was changed just last year. Answers on a postcard if anyone has any ideas.

 

[Frenchy]

Rob,
Sounds like AFM unfortunately was it new or seconhand ? have you had the lid off and looked at the tracks there are a number of things you can do. my 220 is rich on tickover and slightly over on emissions when warm, i have a new sensor to try and Totty is sending me another AFM as i have done the cleaning up of the tracks and repositioing of the arm on the AFM.
3 bar FPR and chips have caused it too run rich at start up so suspecting the sensor as it is acceptable when warmed up.
If it is running rich all the time and ws fine beforehand it points to the AFM.......................Got £500 spare ? there is a Vitesse MAF kit on e bay at the mo !

 

[bighead]

I maybe wrong but is there not a screw that one can adjust the airflow near/by the airflow meter ??

 

[robwright]

On turbos there is no way of adjusting the mixture. I believe there are on other models but not sure. Mark the AFM was second hand but is actually performing well. Having just been scouring the manual and my diagrams I do have one thought. The only thing I didn't check when I installed the AFM was the reading of the air intake sensor, which is mounted in it. I think I will check this in the morrow. It's quite easily done. BTW if you want to change the DME NTC coolant sensor the easiest way to do it is to remove the airbox and the small flexible pipe between the oulet from the block and the other rigid pipe it is linked to. Still a bit fidly but access is OK and a far better alternative to removing the inlet manifold.

 

[Frenchy]

You are not wrong there is an adjustment on the front right hand of the AFM usually under a blue or red plug which requires an allen key to adjust anti clockwise foR leaning i think..........but check.
Forgot about that DOH !

Carbenet Sauvignon !!

[]

There i was egging Rob to get rid of £500 to get a Vitesse MAF kit .

 

[robwright]

Mark I just headed out to the garage and had a good look at the old AFM I took of last year and there is definitley nothing adjustable on it. As for the Vitesse MAF I would absolutely love it but £500 just isn't in the kitty at the minute. It doesn't just stop there either does it? The car would need a remap to suit as well. Either that or change all the injectors. Incidentally what poundage (is that really a word) are the stock 220 injectors?

 

[944Turbo]

There is an idle mixture screw might be under a cover (its a bypass) have you got a pic of the afm? IIRC its near the front end.
Tony

 

[robwright]

Just nicked a couple of the interweb.

 

[944Turbo]

Round hole at the bottom right has an allen headed adjuster (possibly 4mm) mine was hard to spot as very cruddy that might be under a plastic plug,
Tony

 

[Jonny944CS]

Guys, here is an extract from the manual for completeness:

 

[robwright]

OK guys I completely retract my previous staement about there being no mixture adjustment on the turbo AFM. I have just been out and carried out the adjustment on mine. It must have been tinkered with before as there was no cover on the bore to access the screw. A few turns with a small allen key whilst running and I adjusted the mixture to read 14.2 on my AFR meter. This equates to around 0.6% CO, which is the factory reccomended level from the manual. I really can't believe it was that simple. Of course it does help to have an on board AFR meter (invaluable in my opinion) or your own exhaust gas analyser [] I shall wait a while then go and check it again from cold to be sure it is set right. My only question would be that as it is described as idle CO level setting in the manual then the adjustment will only affect the idle mixture? Surely under normal driving conditions the AFM will continue to do it's thing normally?

 

[Jonny944CS]

ORIGINAL: robwright

My only question would be that as it is described as idle CO level setting in the manual then the adjustment will only affect the idle mixture?  Surely under normal driving conditions the AFM will continue to do it's thing normally?

Correct, you are just setting the idle fuel mixture.

As soon as the throttle moves, the idle switch on the potetiometer should trigger the DME to switch the map over to taking readings from the flap position.