Whats the best way to tell if your running lean or rich?

[K.C. 5.0]

i was going to take it someplace that has a diagnostic computer. But before I did I was wondering if anyone had another way to check this out.

------------------
95gt 80k, MSD 6AL, MSD coil, pulleys, fpr, cold air kit, off road h-pipe, flowmasters, 3.73, 9mm wires, mega bite jr lowers, kennybrown subframe connectors, edelbrock performer intake, 70mm TB, 73mm C&L, 24lb injectors Aluminum Driveshaft, Tri-Ax shifter.

[LX XLR8R]

read your plugs or buy an EGT gauge and check your temp at WOT

------------------
1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

[Rick 91GT]

The best way would be a wide ban O2 unit either installed on your car (expensive, but the ultimate tuning device) or you can have it done at a dyno.

Reading the plugs is the easiest way, go out and run at WOT then try not to let the car idle long and pull the plugs. WHITE is LEAN, BLACK IS RICH. If it is really rich it may also blow black smoke.

The EGT gauge is also good but I have no idea what temp a NA car and a blower car should run? Anyone know this?

------------------
Check Out My Site 91GT,Holley SysteMAX II Kit-Heads 2.02" x 1.60" port matched to a 1262,Anderson N-61,24#,76mm C&L,Full MAC, No A/C or PS or emissions, 12" K&N Filter,RNH PERFORMANCE Ram Air,Ron Davis Radiator,Full Suspension, SPEC stage III clutch, Lakewood SFI bell, S&W 8pt "X" brace,JAZ seats,3:73's,Welds..etc,4:30's and 31 splines coming very soon!
<B>12.16 @ 113.5, 1.78 60ft..no traction in the 90 degree

[This message has been edited by Rick 91GT (edited 09-10-2001).]

[This message has been edited by Rick 91GT (edited 09-10-2001).]

[LX XLR8R]

ask jeff chambers for this one but i am pretty sure he said 1340ish for NA

------------------
1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

[Chevyguy]

Somewhere buried in the EEC-IV diagnostics is a test for O2 sensor readings Lean or Rich. One of the KOER tests, My Chiltons book described it to some extent. I have not mastered that system yet, much more complicated than my old GM TBI system in my former daily drivers.

Duno if that would help your problem just my 0.02

------------------
Frank W
90 5.0 LX coupe Daily driver. Silencer removed, K&N filter. Flexalite fan, 3 core radiator. FMS flywheel and Clutch, FMS blue wires Energy Suspension end links
88 Notch 2.3L 5 speed Parts/beater car My two Notchbacks

74 Chevy Laguna Type S-3 305 Finally fixed getting a 454 to put in garage
<A HREF="http://www.chevellepages.com/folingo" TARGET=_blank>www.chevellepages.

[LX XLR8R]

they way that you use the o2 sensors is just buy using a voltage gauge..thats all the a/f meter is..its a voltage gauge with pretty lights..i forget the exact #'s but just try looking for them..i see them all the time just cant forget where on the web

------------------
1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..
AIM=onesillynotch

[silver_pilate]

I know I'm running lean...plugs white with slight orange tint to ceramic of plug. I don't have a FPR, so what can I do to even it out?? Adjust the timing??

--nathan

------------------
--silver_pilate

'91 GT, Built 306, Wolverine 1087 cam, ported Windsor Jr. Irons, and all the goodies...click the link to the left to see a full list of my mods...

Tried and True 302 Being Built to Outrun You! heh heh heh...
--Texas Panhandle--
Check out my site

[Rick 91GT]

If you are running lean you need to get a larger injector, the FPR will only change it till the computer goes back into closed loop. The increased pressure of the fuel will help but the true way would be larger injectors. You could also back off the timing, it will help.

Orange on a plug could be rust? Charcol brown is what you want.

------------------
Check Out My Site 91GT,Holley SysteMAX II Kit-Heads 2.02" x 1.60" port matched to a 1262,Anderson N-61,24#,76mm C&L,Full MAC, No A/C or PS or emissions, 12" K&N Filter,RNH PERFORMANCE Ram Air,Ron Davis Radiator,Full Suspension, SPEC stage III clutch, Lakewood SFI bell, S&W 8pt "X" brace,JAZ seats,3:73's,Welds..etc,4:30's and 31 splines coming very soon!
[b]12.16 @ 113.5, 1.78 60ft..no traction in the 90 degree

[FdMust88]

This was taken from the Autometer.com website. So all you really need is a voltmeter to give you an idea if you are running lean or rich..

A/F RATIO METER & OXYGEN SENSOR OPERATION

This is normal operation for most computer controlled vehicles.
The A/F Ratio Meter is a voltmeter with a range of 0 to 1 Volt. The meter displays the output voltage of the vehicles oxygen sensor through 20 LED's. The first LED will come on at a voltage of .050V, the second at .100V, the third at .150V, etc.

LEAN RANGE: Four red LED's (.050 to .249V)
STOICHIOMETRIC RANGE: Ten yellow LED's (.250 to .749V)
RICH RANGE: Six green LED's (.750 to 1.000V)

The stoichiometric (STOICH) air/fuel ratio is the chemically correct ratio, theoretically all of the oxygen and all of the fuel are consumed. The mixture is neither rich nor lean. However, due to the fact that combustion is never perfect in the real world, there will always be a small amount of oxygen left in the exhaust. This small amount that is left is what the oxygen sensor measures. The smaller the amount of oxygen that is left in the exhaust, the richer the A/F ratio is, and the higher the oxygen sensor voltage is. The on-board computer or Powertrain Control Module (PCM) monitors the voltage from the oxygen sensor. If the PCM sees an oxygen sensor voltage greater than .450V, it immediately starts to reduce the amount of fuel that is metered into the engine by reducing the on time to the fuel injectors. When this happens, the A/F ratio starts to go in the lean direction, and the oxygen sensor voltage starts to go down. When the voltage drops below .450V, the PCM immediately starts to increase the fuel metered to the engine by increasing the on time to the fuel injectors to produce a richer A/F ratio. This occurs until the oxygen sensor voltage goes above .450V. This repeating cycle happens very fast (many times per second). The PCM is said to be in closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. This A/F ratio produces the lowest harmful exhaust emissions, and allows the catalytic converter to operate at peak efficiency, therefore reducing the exhaust emissions further.

Since the oxygen sensor output is non-liner and very sensitive at the stoichiometric A/F ratio it will cause the A/F meter LED's to bounce back and forth rapidly. A very small change in A/F ratio causes a large change in oxygen sensor voltage as can be seen on the graph. This causes the A/F ratio meter LED's to rapidly cycle back and forth, and is normal operation when the PCM is in closed loop and trying to maintain a stoichiometric A/F ratio.


The oxygen sensor is very accurate at indicating a stoichiometric A/F ratio. It is also very accurate at indicating an A/F ratio that is richer or leaner than stoichiometric. However it can not indicate what exactly the A/F ratio is in the rich and lean areas due to the fact that the oxygen sensor output changes with the oxygen sensor temperature and wear. As the sensor temperature increases, the voltage output will decrease for a given A/F ratio in the rich area, and increase in the lean area as shown on the graph.

During wide open throttle (throttle opening greater than 80% as indicated by the throttle position sensor) the A/F ratio will be forced rich by the PCM for maximum power. During this time the oxygen sensor outputs a voltage that corresponds to a rich A/F ratio. But the PCM ignores the oxygen sensor signal because it is not accurate for indicating exactly what the A/F ratio is in this range. The PCM is now in open loop, and relies on factory programmed maps to calculate what the on time of the fuel injectors should be to provide a rich A/F ratio for maximum power. The A/F ratio meter should indicate rich during this time.

During hard deceleration the PCM will command an extremely lean mixture for lowest exhaust emissions. This may cause the A/F ratio meter not to indicate anything. The A/F ratio is so lean that it is outside the range that the meter will indicate.

[FdMust88]

This was taken from the Autometer.com website. So all you really need is a voltmeter to give you an idea if you are running lean or rich..

A/F RATIO METER & OXYGEN SENSOR OPERATION

This is normal operation for most computer controlled vehicles.
The A/F Ratio Meter is a voltmeter with a range of 0 to 1 Volt. The meter displays the output voltage of the vehicles oxygen sensor through 20 LED's. The first LED will come on at a voltage of .050V, the second at .100V, the third at .150V, etc.

LEAN RANGE: Four red LED's (.050 to .249V)
STOICHIOMETRIC RANGE: Ten yellow LED's (.250 to .749V)
RICH RANGE: Six green LED's (.750 to 1.000V)

The stoichiometric (STOICH) air/fuel ratio is the chemically correct ratio, theoretically all of the oxygen and all of the fuel are consumed. The mixture is neither rich nor lean. However, due to the fact that combustion is never perfect in the real world, there will always be a small amount of oxygen left in the exhaust. This small amount that is left is what the oxygen sensor measures. The smaller the amount of oxygen that is left in the exhaust, the richer the A/F ratio is, and the higher the oxygen sensor voltage is. The on-board computer or Powertrain Control Module (PCM) monitors the voltage from the oxygen sensor. If the PCM sees an oxygen sensor voltage greater than .450V, it immediately starts to reduce the amount of fuel that is metered into the engine by reducing the on time to the fuel injectors. When this happens, the A/F ratio starts to go in the lean direction, and the oxygen sensor voltage starts to go down. When the voltage drops below .450V, the PCM immediately starts to increase the fuel metered to the engine by increasing the on time to the fuel injectors to produce a richer A/F ratio. This occurs until the oxygen sensor voltage goes above .450V. This repeating cycle happens very fast (many times per second). The PCM is said to be in closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. This A/F ratio produces the lowest harmful exhaust emissions, and allows the catalytic converter to operate at peak efficiency, therefore reducing the exhaust emissions further.

Since the oxygen sensor output is non-liner and very sensitive at the stoichiometric A/F ratio it will cause the A/F meter LED's to bounce back and forth rapidly. A very small change in A/F ratio causes a large change in oxygen sensor voltage as can be seen on the graph. This causes the A/F ratio meter LED's to rapidly cycle back and forth, and is normal operation when the PCM is in closed loop and trying to maintain a stoichiometric A/F ratio.


The oxygen sensor is very accurate at indicating a stoichiometric A/F ratio. It is also very accurate at indicating an A/F ratio that is richer or leaner than stoichiometric. However it can not indicate what exactly the A/F ratio is in the rich and lean areas due to the fact that the oxygen sensor output changes with the oxygen sensor temperature and wear. As the sensor temperature increases, the voltage output will decrease for a given A/F ratio in the rich area, and increase in the lean area as shown on the graph.

During wide open throttle (throttle opening greater than 80% as indicated by the throttle position sensor) the A/F ratio will be forced rich by the PCM for maximum power. During this time the oxygen sensor outputs a voltage that corresponds to a rich A/F ratio. But the PCM ignores the oxygen sensor signal because it is not accurate for indicating exactly what the A/F ratio is in this range. The PCM is now in open loop, and relies on factory programmed maps to calculate what the on time of the fuel injectors should be to provide a rich A/F ratio for maximum power. The A/F ratio meter should indicate rich during this time.

During hard deceleration the PCM will command an extremely lean mixture for lowest exhaust emissions. This may cause the A/F ratio meter not to indicate anything. The A/F ratio is so lean that it is outside the range that the meter will indicate.