moalaska

Ok so trying to track down my running rich and issue. I jammed my multimeter probe into the black wire at the o2 sensor plug with it plugged together and took voltage readings and cross referenced it with my wideband. This is what I got

.443 volts at 9.5 afr
.46 10.5
.56 11
.66 12
.73 12.6
.81 13
.83 13.2

if i understand correctly the narrow band should read about .45 at stoich. It was already reading This at startup at 9.5 afr. So it was reporting lean when its actually rich. When my wideband started reading stoich, still in closed loop, the voltage readings started jumping all over between .17 and .7. Once it reached operating temp and dme started go ing off the narrowband, the afrs went down to 13s. So if I understand This correctly, the o2 sensor was reporting lean when it wasn't, computer dumped more fuel into mix which created rich afrs. And narrow band still. reporting lean im figuring it is limited to how much adjustment it does. If I take narrowband out of loop by jumping my idle stabilizer ports and forcing dme into closed loop and preset maps, my afrs are perfect at idle. So you guys think i needa new o2? Also i checked voltage going to narrowband it was 13.8.

Tom M'Guinn

I think you may be saying "closed loop" when you mean open loop? Closed loop means when the narrowband is working and continually adjusting the mixture to keep it at 14.7. Open loop means the DME is running straight off the maps without adjustment from the narrow band O2 sensor.

Hard to make much of your numbers. Was the car warmed up when you were getting the numbers you posted? O2 sensors take a while to warm up themselves, so reading them on a cold start motor won't give you useful info...

With your car fully warmed up, and nothing disconnected or jumpered, what are you seeing on the wideband AFR?

moalaska

Those numbers were from cold start to warm taken maybe every 20 seconds or so So right when i started car, wideband was reading 9.5 and narrowband was putting out .443 volts. According to what i read .45 volts from the narrowband is stoich.
when car was warm right before dme started reading from the o2, the narrowband readings started fluctuating crazy
When dme started going off what narrowband said, it the narrowband was reading .8 which indicates lean but it wasn't lean. So it started dumping more fuel in when it wasn't needed. Make sense?

Tom M'Guinn

With your car fully warmed up, and nothing disconnected or jumpered, what are you seeing on the wideband AFR?

The O2 sensor doesn't work until it warms up. Testing it right after you start the car will not tell you anything useful. Also, .8v means it's rich, not lean. Have you tested the car when warm with the O2 sensor disconnected? Have you tested the DME temp sensor?

moalaska

When fully warm, the wideband is reporting around 13 afr idle which I believe is accurate. If I disconnect the narrowband it goes rich to like 11 afr. The dme temp sender is new but i have another new spare i could swap in and see if its faulty. I guess I could try measuring o2 voltage at the dme and make sure its recieving proper voltage.

Tom M'Guinn

Ok, so that means your car is running rich and the O2 sensor is working to lean it out. The closed loop O2 system makes only minor adjustments, however, and can't lean it enough to get it to 14.7. While it's far from a conclusive test, that info alone would make me look somewhere else for the source of your rich running.

Does it run rich on the road too, or just at idle?

How is the ground wired for your Vitesse MAF? If the ground is not good, the car will run rich. You might try running the MF ground straight to the neg battery terminal to test.

How's the ignition? Weak ignition/missing can give unpredictable AFR's.

Have you checked the TPS and/or the MAF voltage on Pin 7 of the DME? Both worth trying. Also worth confirming fuel pressure and that the vacuum line to the FPR has vacuum and no leaks. Also worth confirming the KLR is not incorrectly triggering the WOT signal.

What's the last thing you did to the car before this started?

moalaska

Right now it seems to be running rich at idle and i think somewhat lean under load will have to get my cv axle put back in to test. Something is causing it to falsely go rich if i do the jumper wire for idle it runs near perfect stoich idle.

the maf must be one of his early ones. The instructions say to splice the ground wire in with like 3 othet wires. I went ahead and grounded it to the driver side close to fender next to another ground wire. I could run it to battery i wad thinning about that.

msd blaster coil and new plugs they were fouled from the rich running i put new ones in spark seems a little bit weak

tps microswitch function is tested good at the switch

full throttle im not sure of

​​​​​​​fuel pressure regulator is adjustable and i set it engine off warm to 3 bar

markl951

The stock, narrowband O2 sensor is not really a sensor in the way you're trying to relate voltage to AFR. The stock O2 sensor's dynamic range is so low it should really be thought of as a switch. When the fuel mixture is rich it generates a voltage of about 0.9V. When lean, it generates a voltage of approximately 0.1V. The closed loop controller of the DME uses these two voltage levels as an error signal to drive the average AFR to a stoichiometric point which happens to be a sensor output voltage of 0.45V.

If the DME is running in closed loop mode and you measure over a long enough period of time with your (high impedance) digital voltmeter you'll see an average value of .45V. On an oscilloscope you'd see the voltage switching back and forth between .9V and .1V. If you measure something other than that, the close loop controller has probably run out of control or adjustment range and can no longer correct the injector duty cycle enough to keep the AFR at the .45V average value. If our cars were OBD-II, the check engine light would come on to tell us that.

I'd recommend reading this article on the subject for more info.

moalaska

Hmm ok. Well as it was warming up the voltages were above .45 steady. Went from .45 to .8 slowly climbing. Then when the car got fairly warm and the wideband reached about 14 afr the narrowband voltages started oscillating like you describe between .1 and .9 rapidly. Then after about 3 minutes it went steady again. So maybe it isn't functioning properly

moalaska

Okay had some time today to work on my car. I replaced my Nearly New temperature sensor with another brand new one. I also ran a dedicated ground for my MAF to the negative battery terminal. Once my car warmed up it hovered right around 14.7 and stay there. I can probably put the ground back at the other location and that would tell me if it was the temp sender or the ground. Don't know how it will act under a load there yet I have to get my CV axle in there

markl951

You can test the DME Temperature Sensor. Clark's Garage is one place to look for how you can do this.

fast951

As per our private emails, it's more than likely a ground issue. Very common on the 951! Will be interesting to know what you determine as the root cause.