Asarus

Hi guys,

I currently have the guru 18-psi chips installed with an almost stock wastegate that holds only 13-psi. I didn't get time yet to install the accuboost, bypass the CV and change (or shim) the wastegate.

I installed an Autometer Cobalt AF gauge connected to the DME (pin 24)


I also have a Lindsey 3" exhaust with flowmaster 50 muffler. My adjustable FPR is set to 47 psi (a bit more than normal because of the lean indication)

According to my AF gauge, i run a bit lean (lean leds while cruising, stoechio when WOT and never rich). According to my personnal feeling, i run way too rich : 390 kms before to empty the fuel tank and a fuel smell when someone follows the car. The car is not running really great at all (probably slower than a 944 S2 currently)

I don't really know what happens and have some ideas :

1* the AF gauge is not accurate : i don't think so because my volmeter indicates the same as the gauge shows... the signal was tapped from the pin 24 from the DME

2* the lambda sensor is dead ? maybe so...

3* the adjustable FPR is faulty ? i have the lindsey fuel gauge installed and when checking with the fuel pump running only (connect pin 30 and 87b together instead of the DME relay), it's still correct and keeps the pressure i asked. On idle, the gauge indicates 40/42 psi (normal)

What do you think ?

OriginalSterm

vacuum leak? periodically stuck injector?

lambda sensors do go bad, or depending on where the wiring runs could have a short in the wires that shows strange signals under load. my O2 sensor wires got melted together by the exhaust, which ended up blowing my fuel pump fuse. climbed underneath and find the insulation was melted away, and the wires were also bare in a few spots. just a possibility...

Asarus

My injectors are good (i'm sure because they have been cleaned and checked before to be used) and i have no idle problem or any hesitation (always running with my 4 cylinders)

Vaccum leak : i didn't notice any currently and i have double checked everything (the motor was rebuilt 2 months ago)

Will a blown O2 sensor still indicate some 0 to 1v values that "looks" coherent ? It's like if my O2 sensor was indicating always too low (lean instead of stoechio, stoechio instead of rich). The AF gauge indicates leaner when i put the AC on also... (i guess it's normal)

Duke

I would suspect the 02 sensor.
But you never know with the 0-1 volt A/F-meters...

rage2

If your car is running like crap, smelling like fuel, and showing lean, it means one of your plugs is fouled, or you've lost compression in one of the cylinders. If one of the cylinders isn't firing, the O2 sensor will show a lot leaner than it really is because the oxygen isn't being burned, and there'd be TONS of fuel getting dumped out the exhaust.

I've had this happen when I went too cold on a set of plugs, and the car ran on 3 cylinders. Pull and inspect the plugs, it'll be very obvious which one is bad.

Sam Lin

Narrowband O2 is worthless, your readings are a crapshoot - get a real reading and see what's actually going on.

Sam

Asarus

I will check the spark plugs tonight... they have only 3.000 miles. The car always run on 4 cylinders anyway. I don't think i have a compression problem as the whole motor was rebuilt 3.000 miles ago but i'll ask to a garage to lend me a compression tester.

Sam : what do you recommand to check the AF ratio with accuracy instead of the narrowband O2 ?

Duke : i currently think like you... i suspect my O2 sensor to be the problem as the autometer gauge indicates exactly what my voltmeter indicates...

Mike1982

Oh yea, moving one bar towards the lean side is normal. Happens to me all the time. I REALLY need to get a WB02 sensor as well.

Duke

Asarus, get a wideband o2 so you can see the exact A/F ratio. It's probably the best $300 I spent on my 951!

Check these sites out:
http://wbo2.com
http://www.plxdevices.com
http://www.innovatemotorsports.com/

Asarus

Duke : if you have informations on the wideband you bought, the price and the installation procedure, i may be interested in...

UK952

Before you blame the guage there is obviously something else going on, might be a good idea to install the accuboost if you are only running 13 psi on 18 psi chips I think you will be very, very, rich. Get close to the right numbers and the guage might spring back to life.

Tony

Asarus

Sure, i ordered the accuboost and i'm waiting for the delivery but anyway there is something wrong currently as my gauge (or the O2 sensor probably) indicates lean/stoechio when i run rich...

Duke

Aha I missed that. Tony you're probably right, as the 0-1 volt A/F gauges can show very strange things when either very rich or very lean.

An even better reason to get a WBo2

I have a PLX M300. Very easy to hook up and use. Besides the need for a new bung in the exhaust to mount the sensor, it only needs a 12 volt cable and ground.
It's also a very good package which makes it easy to build a nice gauge panel, here's the panel I built:

hosrom_951

Duke: The PLX M300 looks pretty nice

B951S

PLX now do a nice 2-1/16" gauge with a digital readout and sweeping LEDs. Check out their site. I just got one, works great.

www.plxdevices.com