Mrmerlin

Has anyone tried this procedure??

To adjust the MAF you're supposed to use an exhaust gas analyzer. The car is brought up to normal operating temperature, the O2 sensor is disconnected, and the MAF is adjusted until the exhaust gas analyzer reads what it's supposed to. You can do a pretty good job using either an air/fuel mixture gauge or a volt meter instead of an exhaust gas analyzer. Warm the car to normal operating temperature. Disconnect the O2 sensor from the engine management computer, but have the O2 sensor signal output wire connected to an air/fuel gauge or a digital volt meter. If using the volt meter, the positive lead of the meter goes to the signal output wire of the O2 sensor, and the negative lead goes to any available ground. With the engine idling, adjust the MAF until you get the air/fuel gauge to show about a 14.7:1 ratio. That's five of the ten lights being lit on the more common air/fuel gauges. If using the digital volt meter, adjust the MAF until the meter shows around .5 volts. Then you just reconnect the O2 sensor to the engine management computer. If you try to adjust the MAF without disconnecting the O2 sensor from the computer, it won't have much of an effect unless you get to a setting that's so extreme it's out of the computer's adjusting range. If you try to adjust the MAF with the O2 sensor connected to the computer, the computer will just use the information it gets from the O2 sensor to adjust the mixture, and your adjustment at the MAF will just be compensated as the computer brings the mixture back to where it thinks it should be. When you floor the car, the system goes into open loop mode, and the computer ignores any signal from the O2 sensor. It just uses a preset maps stored in the computer then.

PorKen

Just buy a Blink'r...

(There's a thread somewhere here where some fool tells how to make your own LED feedback circuit, BTW.)

The mid point of the CO adjustment is ~380 ohms. CW richens, CCW leans. It's not a direct resistance to the MAF circuit, only a voltage input which is turned into a number by the LH to modify the fueling calculation.


BTW: On any S3 I recommend using colder plugs, and gapping to them to 0.032". The wider gap is more efficient. (On a S3, resistor plugs will handle up to ~0.035" before you get high rpm losses.)

Mrmerlin

Thanks for the reply Ken my MAF was set at 497 OHMS and the car failed with a high CO.
actual was 23.9 and max is 20.0, will colder plugs help with the emissions setting??
It has WR7DC now, and they are the copper tips.
I am going to try some MAF adjusting i will reset it to 380 and see where it takes things,
I will also replace the plugs if these ones I have are not what you suggest.


BTW I made a better tool for MAF adjusting I took a 14in. piece of 3 mm vacuum hose with the thread wrapped outside ,
and cut off a piece of 3mm allen wrench about 3/4 of an inch long and with a few drops of super glue, glued the allen into the hose, the tool easily turns the adjustment screw.
To fit it into the MAF a long set of needle nose pliers can be used to fit it to the MAF adjuster screw,
then it will feed itself into the hole.
Just thought you might like this info as the tool you made is sort of unwieldly.
Thanks again for sharing your wisdom, Stan

PorKen

Colder won't help, but the wider gap may.

Mrmerlin

Ok Ken I will check the gaps,
so what plug do you suggest for the 86 do you have the number?? Thanks

BIMMERMIKE

WR6DC or WR5DC is what I'm using with Kens' chips

JHowell37

Stick WR7DC. If you're having trouble passing emissions you don't put in colder plugs.

How old is your 02 sensor?

For the purposes of emissions, you can always use the MAF from your '88.

Mrmerlin

Ok I will open the gaps on the WR7DC plugs ,it appears as thopugh they are set at .028 I will open the gap up to .032
The MAF and O2 sensor both appear new as the PO was chasing running issues and went about replacing all kinds of parts to get the car to run correctly it took replacing the engine harness to get it running as it should

zoltan944

The nice thing about Porken's blink'r is rather than guess on numbers with the MAF you correctly set the MAF based on the O2 signal. If your O2 is good you are going to set the MAF near perfect regardless what the ohms end up being. But measuring with voltage if unsure about O2 is good too, but then will the O2 plugged back in aid you in failing the Smog?

Did you check the temp2 as well?

Mrmerlin

Temp 2 looks new, but i will test it

Mrmerlin

Temp 2 sensors is working .
I went and reset the MAF to 380 then regapped the plugs (WR7DC Bosch copper tips,) most of the gaps were set at between .020 to .026 so I made them all .032 in.
Started the car and let it warm up then unplugged the O2 sensor and was getting approx .058 volts I adjusted the MAF to get the sensor hunting between .047 to .051v .
The exhaust smells different than it did from before any other adjustments were made.
Anyway I rechecked the MAF and its now reading 375 OHM .
So I left things alone, it seems to be running good now.
Is there anything else i can do before i go for a retest??
Could the hiflow cats have anything to do with the rich running.
Could the way the car is driven on the dyno have anything to do with its running it seemed to have the RPMs pretty low while the test was being performed about 1300 RPM on one of the sheets I got

PorKen

Check the return hose from the FPR/fuel pressure. If the hose is too long it will kink and drive up the fuel pressure, resulting in rich running.


Bridge B & C and set the base idle with the engine fully warmed up. The CO setting is sensitive to having the correct idle speed.

Mrmerlin

FPR fuel hose is new and its the stock size no kinks.
I will recheck the idle thanks Ken as it was it idling right at 700

JHowell37

Any exhaust leaks upstream of the O2 sensor?

How does it run? Do you drive it like a ***** or with the confidence and swagger of a warlord? I have to ask because this place is rampant with manginas. Sometimes an Italian tune-up can be helpful.

You said your car showed 23 with a limit of 20. Is this GPM?

Have you tested your TPS to make sure it functions properly?

Mrmerlin

No obvious ex leaks, seems to run good it likes to be revved and thats how its driven like i stole it
23 GPM i believe thats grams
TPS checks out correctly