Porsche Enthusiasts Club Forum

HI All,

Submitted my 944 2.7 project for MOT this morning and it failed - but not on too much and given it stood for 4 years or so and I've replaced the sills etc - I was quite pleased.
Failure points were:

Illegal front and back number plates (!)
n/s front brake binding (probably a good run would sort this)
A couple of non functioning lights - again probably corroded connectors
and...emissions.

I had 6% CO whereas the legal limit is 3.5%
Reading on this forum and others - a good 944 should achieve around 2% CO content/volume

I've read that the usual problems of running rich are:

Failed/failing DME temp sensor
Worn AFM
Plug leads
Spark plugs
and of course air filter

Are there any other causes?

Car had a FSH before layup and it looks like the plugs were very new, Plug leads are unknown (a bit nibbled by rodents though!)
Air filter new.

Car idles and starts fine - it does feel hesitatnt when running on the road - likes it is running rich.
Is the AFM an easy fix? clean? inspect? I have Clarks Garage guide to the AFM but any/all advice welcome!

Thanks

Ian

Ian, if it is miles out, it is probably the AFM. What is the Bosch number of it and I will see if I have a spare one here? Are you getting a bit of black smoke out the back when you first start up from cold?
Alasdair

Can you say that being 6% CO content/volume (i.e. 100% more than legla max and 150% more than expected) is way out - then I guess the AFM is a suspect.
Would the car having stood for a long time (4 years or so) have a bearing on the performance of the AFN?
I'll check part numbers but it is for an 89 2.7 model.
Thanks for the reply!

Ian

HI

Retested my 944 this morning and it passed. However, the emissions (CO) was now down at 0.2% which seems far too lean.
To adjust the previously high emissions (running rich condition) - I replaced the following parts (as per 2.7 parts codes):

DME temp sensor
The MAF unit
New air filter

Previously during the resto on the car, I had changed the injectors for reconned ones for the 2.7 engine. In hindsight, looking at the old MAF, the mixture screw had clearly been adjusted, so I guess its possible that the mixture had been enriched then to account for original faltering injectors(?). Anyway the MAF unit I installed still had the tamper proof plug installed so i assume it was still factory set.

So- 0.2% is too lean I think and the engine was running a little warm too - what are folks thoughts on here?
Tweak the MAF mixture a bit to enrich the mixture?

Tnanks for thoughts

Ed

Yup tweak the screw to get around 1.8%-2.0% It should be a bit more economical as well.

PS what was the issue with the plates?

Number plates - to quote from the failure sheet:

"Front/rear - registration plate background overprinted or shadowed with text"

The plates had the porsche badge on the first inch or so and '944' in repeated light colour in the background as a watermark style feature....

Anyway - just got new plates made up
CHeers
Ed

Me thinks I'll be changing mine before the MOT & change them back afterwards then...