Porsche Enthusiasts Club Forum

Hi Folks,

I've got my 944 Turbo back on the road now and noticed that it seems to be running very rich -

• Very smelly exhaust fumes
• High CO and HC readings on MOT
• Intake manifold very hot
• Previous oil was contaminated with fuel

I've replaced the fuel pump check valve (porsche item) and also the fuel filter, couldn't smell any fuel in the FPR vacuum line.

I've ordered a new Bosch DME temperature sensor as they are pretty cheap, but I'm going to test the existing one to confirm if that is the issue.

Can anyone recommend a not too expensive fuel pressure test kit? Or am I better off making my own? I see most of the test kits on Amazon etc come with schrader fittings whereas the test port on the Porsche is an M12 x 1.5 standard fitting.

Will also be checking the vacuum lines, the heater controls work and it does boost (and holds boost) but feels a bit hesitant (I'm guessing this is down to overfueling).

I also have the option of sending off my injectors to get them cleaned and tested but want to minimize time the car is immobile.

Here is a history of my emissions tests below - interestingly Promax replaced the vacuum lines and the O2 sensor coding plug at the back of the engine (in 2013 as I failed the MOT on emissions). I do have an O2 sensor but it is disconnected. I seem to remember having a chat with Andy at the time, so maybe I just need to replace the O2 sensor? although I've read that non-CAT 944s didn't have an O2 sensor and also that others have used the coding plug with no issues...

Date Mileage CO % vol HC
17/03/2008 147294 0.49 51
18/05/2009 157164 0.512 61
08/05/2010 167141 0.597 55
14/05/2011 178494 0.11 55
12/05/2012 190364 1.746 53
10/06/2013 201814 2.43 140
22/05/2014 204929 0.432 55
26/07/2019 205058 3.104 165

Thanks

AFM or connections to it. Also if it's not been used much that wont help. Do you have an AFR gauge?

Good shout - I've been reading the old posts on here, rennlist and PCGB about rich running

The AFM plug is a bit loose so will inspect the contacts.

Also I noted when getting the engine running initially that it idles fine with the fuel pump fuse removed (but dies if you try and increase the revs), I'm pretty sure that before I replaced the check valve etc that it would die pretty soon after removing the fuse.

Any suggestions on a fuel pressure gauge?

Also what are the thoughts on the coding plug installed in the O2 sensor plug with the O2 sensor disconnected? (although it passed a previous MOT fine with this installed and low CO / HC)

No idea about the coding plug. I do recall a while back changing out the FPR and doing other stuff to try and remedy a very rich car. In the end it was oxidisation on one of the AFM plug connectors. One of the pins is critical for fuelling and the car will run rich if the sensitivity of the wire becomes dulled. I am running a SciVision maf but it connects via the original AFM plug and this is where the issue was. Also on a standard turbo AFM setup the loom bends right back on itself just before plugging into the AFM. This is also known to cause problems after many years. Check out your wiring from that bend and also clean up the connectors on the AFM and AFM plug. I used DeOxit and it worked a treat. Good luck.

I have a spare working 3 bar FPR if needed. You would need a mechanical gauge wired up to get a reading on the fuel pressure. Swapping out a known working one would rule out the FPR. As I have an AFR guage i can see if its running rich or lean from the cabin.

Stuart

Hi Stuart,

Thanks - going to clean the AFM connector and see if I can get a pressure gauge setup.

Interestingly I did a quick search for a replacement FPR and it appears they are no longer available so god knows what I will do if it is faulty.

Mine is the later type with the screw on hose fitting - also showing as NLA in PET2.

Dave

I've got a standard turbo screw on FPR which came off when I changed to the 3 bar set up. I would like to keep it for the eventuality of putting car back to standard if I ever sell it but you could borrow it if need be for testing.

I can see the damper screw on in PET2

944 110 201 04 £317.52

for engines 4411,4412,4441

944 110 201 03 £317.48

for engines 4452


Bosch

0 280 160 258
0 280 160 249

I got the Arnwerx fuel pressure tester, it has the correct union which some don't but the plasic screen melts with petrol, hope he's changed that.

Thanks Endoman - I was looking at that and could knock my own up with the correct fittings. I made a similar pressure testing device for leak testing my watercooling loop on my PC a couple of years ago. Consists of a t-piece with the gauge connected, a hose to connect to the loop being tested and a schrader valve to release the pressure. With the fuel version I have some fuel hose already and just need a gas valve instead of the schrader valve to release the pressure and fluid into a container.

Managed to test the DME temperature sensor tonight and it looks fine according to the figures from Clarks Garage - I tested it at the sensor and also from the DME wiring harness to make sure there wasn't any issues with the wiring harness (same reading at each end).

http://www.clarks-garage.com/pdf-manual/elect-19.pdf

Ambient temp (approximately 17.6C) = 2.85 k-ohms
Engine at first white line (80C) = 267 ohms

I also cleaned the AFM wiring connector as suggested by Stuart - the blades did look pretty dirty and I got quite a lot of dirt off with some Deox Gel and several cotton buds, also the spring on the connector wasn't located correctly so also sorted that and now holds on more securely.

Ordered a cheap fuel pressure test kit from Amazon - will see what adaptors come with it but as I said above I may be sending this back and making my own if none of the adaptors are correct size.

US PRO 20pc Petrol and Diesel Fuel Pump Pressure Tester Meter Kit Set 0 - 1... https://www.amazon.co.uk/dp/B076HYQ77P/ref=cm_sw_r_tw_dp_U_x_MfFqDbEWFKJVE

Also picked up a vacuum tester seeing as it was only £12 and will test for leaks.

I fixed a rich running / fuel in oil problem on my S2 earlier this year. After chasing though all the cheap fixes, it was the AFM. I had it tested and rebuilt, all fine now.

Hi Ed - where did you get it tested and rebuilt? and if you don't mind how much did it cost?

Have a look at ebay auction no. 173592972948

Awesome thanks Scott - I had already bookmarked that companys website but it didn't have any prices on there so now I know how much the damage is

Checked the fuel pressure today using my cheap pressure gauge from Amazon with an adaptor off ebay -



With the Fuel Pump jumpered and the engine not running = 2.6 bar

With the engine running = 2.2 bar

Leakdown test it held 2.4 bar for 20 minutes after the fuel pump was shut off

I also removed the fuel rail and put each of the injectors into a container to ascertain if one or more were leaking, I pressurized the system via the fuel pump and then switched it off and left it for a good 2 hours and all of the containers were dry apart from a tiny bit of dampness in injector #1 container but that may have just been a bit of oil that was on the o-ring.

I also removed the vacuum lines from the FPR and FPD and they were bone dry with no fuel dribbling out or in the line.

I think I will reserve judgement on next steps until I get chance to do another road test as I've cleaned up those AFM connections and want to see if it just needs a bit more running to clear out any deposits in the fuel and exhaust system.

EDIT: I've also got a new air filter I'm going to stick in even though the one in there has only done a few thousand miles and looks pretty clean.

I changed the air filter and went for another drive and although it drove OK it still smelt very rich and hesitated a little (tiny bit). Car did boost fine and several times shot off like I remember

So next on the list was to check the AFM...

BINGO! :thumbs: I found an issue with the AFM when it was fully open at maximum air flow the voltage dropped completely moving from about 99% to 100% open and was repeatable. I'm guessing this is the cause of the intermittent power loss at WOT. I got my trusty pencil eraser out and cleaned the track on the potentiometer. Also gave the metal contacts a good clean with some 5000 grit paper and it was fixed and now reporting highest voltage at fully open and increased gradually with no flat spots between 0-100%. The air temp sensor also checked out OK reporting the correct k-ohms for the ambient temperature (2.17 k-ohms).



I used the testing guide from Clarks Garage which utilises a 9v battery for power source -

http://www.clarks-garage.com/shop-manual/elect-22.htm

Next jobs I have is to fit a new Bosch O2 sensor I ordered from Opie Oils, test the TPS (Throttle Position Sensor) and adjust the idle mixture on the AFM.

If I still have an issue then I will suspect the injectors and get them sent off for testing and refurb.