Edman951

Asurus,
To confirm its not the gauge. Check the voltage on the purple wire.
If you only see .50 to .70 vollt at WOT. Then its you car.
If you see .85 to .95 volt at WOT then it the gauge thats wrong.

Did you by the gauge new or used?

It could be the FPR, check on your gauge when you remove the vacum line.
If the reading on the gauge doesn'T move it either you have a bad FPR or their is no vacum on that hose. Check to see if that line is disconnected.
It actually happened to me last week and i has leaning out over 13 psi.
Good luck

Asarus

Hi Edman

I checked the voltage at the purple wire and it indicates the same as the gauge (no more than 0.7 v even when i'm set really rich with 48-psi on the AFPR)
I set up the AFPR back to the original setting for the guru chips : 44 psi
I checked the AFPR vaccum line. I have some vaccum here, no pb..
I changed the plugs for WR6DC ones
I put a plug in the region coding switch. That will use the map #2 on guru chips, so the 15-psi maps instead of the 18-psi ones as i currently have no more than 13-14 psi until i didn't get my accuboost installed.

I assume the O2 sensor is bad and will look at the gauge with care (just to know but without being too confident in the indication...).

I'm gonna make a test trip in the next hours and see how the car behaves, and will let you know

Seb

Asarus

I made my test trip...

The car is working better but not great yet. It looks like it's more difficult when on high rpm, more than 5500 rpm (anyway i still haven't bypassed the CV and i haven't the correct boost level yet).

Here are some videos (MPG format) of the boost gauge, af ratio gauge to show you how it behaves

Cruising - 1.2 Mb - Start slowly and use the 1st, 2nd and 3rd gear - AF gauge display

AF Ratio - 1.7 Mb - Autometer AF gauge display when on WOT. The video starts in 3rd gear at 3000 rpm and stops at 5500 in 4th gear

Boost gauge - 2.2 Mb - VDO Boost gauge - The video starts at 3000 rpm in 2nd gear and ends up at 5000 rpm in 4th gear - The gauge displays in bar so the "1" means 1 bar = 15 psi. The max boost level reached here is 0.9 bar so about 13.5 psi. Sorry, the video is not really good.

PS: the oil temp gauge is not connected yet, so it's normal if you see a very low temp

Can you tell me what you think of this ?
I still have the feeling that the O2 sensor is faulty or maybe not accurate enought to show a good AF ratio. The gauge indicates almost the same thing as when the fuel pressure was set up to 48 psi (instead of 44 psi on these videos) and when i was using the 18-psi maps (instead of the 15-psi maps here) !

Duke

Your o2-sensor is toast!
When cruising or idling when the sensor is warmed up the A/F-gauge should be dithering and swinging back and forth the scale like crazy. OR if the engine/sensor is cold is should display a solid bar somewhere in the rich-scale.

It's not very likely that there's something else but the o2-sensor that is causing this.

Jake951

That WOT A/F display looks worrisome to me. The yellow LED's mean you are staying in the stoichiometric A/F region (14.7:1 +/-). You should be solidly into the green with no more than two green LED's showing at a time. It's much more likely that the O2 sensor is faulty than the Autometer gauge. The gauge is nothing more than a voltmeter with an LED display. Can you try a different O2 sensor? Also, did you ever try using different chips? If so, what was the result?

Asarus

Thanks for your replies

I got the same behavior with the stock chips, except that i got a bouncing gauge (still in the same zone, from lean to stoechio). I guess this is because the stock chips are designed to work with the O2 sensor and adjust the AF ratio with it.

The gauge is ok. I get the same values displayed as i get if i use a voltmeter. That's why i think the O2 sensor is dead.

When cold, the gauge indicates stoechio (the 2nd or 3rd yellow led, so near the lean zone) and after a few seconds, it still indicates stoechio but the 4th or 5th yellow led, so a bit richer...
When warm, it indicates lean/stoechio when cruising and stoechio (but never rich) on WOT. When warm with 48-psi maps, it indicates same as currently (but not rich) !

I will try to get a friend of mine lend me an other O2 sensor but it won't be done before a couple of days or weeks

Edman951

Salut Asurus,

Your gauge seems weird?
It seem to show more leds at the same time then the gauge i used to have.
Maybe others guys on the list can tell us if it looks normal?

But since you are not getting more then .70V its probably the O2 sensor.

If the sensor was working and you had fuel problem, you would probably see the gauge go higher at low rpm compared to now.

Its kinda like the problem i had last week. I was runing lean at WOT. But i had some rich spots on my wideband O2. I was sure it was a weak fuel pump of dirty fuel filter. Because my AFPR was acting normal.
So i desided to replace the pump with a 928GTS the filter and the O2. Since i was not sure what was cossing this leanout at WOT. Anyways those parts where getting old and upgrading the fuel pump was in my plans.
After replacing them the car ran the same.
After more investigation i notice that the fuel pressure was not moving around alot at idle and when i gave some gas. ( up and down a few psi)
Then i notice that the vacum line was broken under the manifold and i was not getting good vacum to the regulator.
Once i replace that hose all went back to normal.
44psi w/o vacum
arond 35 psi w/ vacum connected
And over 44 psi when on boost.

Bonne chance

Asarus

Merci Edman

I checked my fuel pressure and it's still good at 44-psi (with the fuel pump running). On idle, it's a bit lower as stated in the Porsche manual. I think i get about 40-psi on idle. When on boost i don't know because the gauge is under the hood

Should the fuel pressure raise if i accelerate but with no gear engaged ?
When i disconnect the hose going from the FPR to the manifold (on the FPR side) i can notice that the air is sucked from the manifold, so it looks ok and the hose seems also ok. The AF gauge doesn't notice anything when i do that.. but as i said i suspect the 02 sensor to be faulty so maybe it won't change the display even if i disconnect this hose..

Asarus

On this AF gauge here are the O2 sensor values corresponding to the leds (0.050 v for each led) :

* 4 red leds : 0.050v to 0.249 v (LEAN)
* 10 yellow leds : 0.250 to 0.749 v (STOECHIO)
* 6 green leds : 0.750 to 1.0 v (RICH)

So i confirm that the O2 sensor never delivers more than 0.7 v signal

Duke

That is normal on these gauges.

Edman951

Asarus,
The 40psi you see on idle is it with the vacum connected or without?

And if you look at the fuel pressure gauge when everything is connected. Does it go up about 5 to 10 psi when you give it some big shoots of gas?
Normally the fuel pressure should move alot from 18inch of vacum to 0 psi.

Asarus

The 40 psi i saw was with the vaccum connected (at idle, and cold). I will look how the fuel pressure moves depending on the throttle and tell you

UK952

My autometer guage only has at most 4 or 5 Leds lit at one time usually a bright centre one and slightly dimmer ones either side.
Where are you picking up the signal from?
There is a plug at the back of the cylinder head with 3 pins, 2 are male one is female (A) or one male(A) 2 female depending on which end (the sensor or the wiring loom).
If you strip back the insulation on a thin test wire and push it into the pin on its own(A) and reconnect then you can check the voltage of the sensor in the engine bay.
Hope that makes sense,
Tony

Asarus

UK952: that makes sense the voltage on the O2 sensor is the same as what i get on the DME box (pin 24) and the same as what the gauge displays. I checked with a voltmeter. I tapped the signal from the DME box are it's shielded (i followed the Danno procedure from his site : racerx)

FPR: i did some tests :

AFPR set to 44 psi
at idle : 38/39 psi
when accelerating (from under the hood), it goes up to 44 psi and drops to 36 psi then when i stop and is stable at 38/39 psi then
if i disconnect the vaccum line going to the manifold, the fuel pressure raise up to 46 psi (still at idle)

It looks like my AFPR is good and the vaccum lines also. I asked an other O2 sensor to my friend. I should get it in the next days to try

Edman951

So with that test we know that the AFPR is good.
Its pointing more to the O2.
Hope for you its just that.
Good luck