Porsche Enthusiasts Club Forum

So it was MOT day today but it didn't go according to plan. I checked all the lights only to find I had no main beam  which fortunately I traced back to a loose fuse on the hid's. However the problems did not end there upon collection I was informed it failed on emissions CO was 4.03% (fail max 3.5%) HC was fine at 148ppm.

I had noticed my afr reading had dropped over the last couple of weeks to around 12 and I will have a poke around this weekend, check and clean the plugs etc and the wideband sensor, what other suspects should I look at ?

Not sure which 944 you have or whether the mixture can be manually adjusted but my 924 had CO of nearly 7 but a tweak of the mixture brought this down to 0.45. Had to address the idle at the same time to compensate but that was reasonably simple solution given all other readings were fine. Hope this helps.

Mine's a Turbo, thankfully the weather looks good for the rest of the weekend for some tinkering.

As you say, something is causing it to run rich.

It could be:

-It was not warmed up for the MOT
-The coolant tempereture sensor going to the ECU
-AFM

My bet is partially on the AFM. You *can* manually adjust them but this does require someone who knows what they are doing. It could also be down to a bad track but I'd expect other problems with the car.

FWIW my 944 Turbo with no cats managed to fly through the test.

Funnily enough I have ordered a sensor today. I also fitted a new dizzy cap and rotor arm, the cap was quite worn and the rotor arm has been wearing it away on the inside of the cap. When I compared it to the new rotor arm its actually slightly taller.

My K&N filter was also dirtier than it first looked, I spent an hour blowing it with an air line and then when I checked the plugs No.1 was gapped incorrectly and sooty.

I'm wondering about the AFM and I have actually replaced it once I think I might crack it open and take a look at the track.