How will I know when my motor is running too lean?

Wide band is a good Idea, to get a good starting point. I put one on mine before I got the Moates QH. I thought that I was running lean and didn't want to blow my motor up, so I got it first and found out that I was running Rich...

With a stock engine , the computer is smart enough to read the O2 sensor outputs and adjust the fuel injector pulse width and richen or lean the mixture according to the need of the moment.

High flow heads, intake manifold and cam will require larger injectors and a MAF matched to the injector size, OR a custom dyno tune chip burned for your engine combination.

Want to make sure you are OK for now? Then dump the codes and see what the computer says. Codes may be present even without the Check Engine Light (CEL) being on.


Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.





If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus - Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

No, it will just damage your engine..

If you put anything more than gt40- or gt40p heads on top of your motor it would prob be a good idea to upgrade. My bro has gt-40x aluminum heads, e cam and a ported gt40 intake on his with stock stuff. But in my opinion he is prob running his injectors at 100% duty cycle.. It dynoed over 300 hp. And I think about 325 tq..there are formulas out there to figure out injector duty cycle..pretty sure you want to keep it under 80%.. Without turning up the fuel pressure.

7991LXnSHO said:

SO Then I need to do some math.

For when I am too busy driving, what is a good, lower cost Wideband O2 Sensor setup? I have no idea what is junk in this category and what is a good sensor set up. (Auto Tune has worked well on other gauges for other gauges.) I do not want to spend a lot or waste money either!

Click to expand...

You are probably not going to get a good Wideband for cheap. I have an AEM and payed almost $300 for it. a similar Innovate Wideband is about the same price.