89 5.0 running pig rich

[ratio411]

Okay, so our 5.0/AOD combo is running super rich at low rpms.

We dyno'd it the other day, and on every pull it started at 10:1 AFR, and gradually rose until 6k rpms where it peaked at 13:1.
It was a steady rise, not any sort of quick change.
Just a 45* line from 10 to 13, 2k rpm to 6k rpm.

So it is pig rich down low, then gradually leans out to redline.

The dyno operator said the line should be flat, not a 45* slope.

The shop says the only way to clear it up is with a $450 tune (plus initial $250 buy in of a specific chip set they use to interface with the ECM)

Can't afford that!

I can think of a thousand ways to lean out the engine, but the fear is that if we lean out the bottom end, and the AFR slope stays the same, it will lean out the top end to a dangerous level.

One would hope that we could lean out the bottom, and the ECM would see the top getting too lean and richen it out. ??? IDEAS?

 

[88gt373]

my buddy had the same problem with his and he fixed his Lean problem with a tuner chip he got from American muscle.... his is a 5 speed tho and he also needed to lean it out for emissions (we live in cali where smog nazis live!!)... im actually dealing with stupid smog as we speak.....

anyway, after he put the chip is it ran way better and didnt smell that rich at idle either... plus was a great because you can get free tunes from BAMA after upgrades like CAI/mass air, injectors, etc... beats goin to the dyno thats for sure.... why do you wanna lean it out? hows performance?

 

[jrichker]

Before you spend money on an expensive tune spend 2 cents to buy a paper clip. You may have other problems causing your over rich condition.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 3-Jun-2011. Removed the link to BATAuto.com and troublecodes.net instructions on codes and how to dump them. Post the codes you get and I will post 5.0 Mustang specific code definitions and fixes.

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.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. 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 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.
Or for a nicer scanner see http://www.midwayautosupply.com/p-7208-equus-digital-ford-code-reader-3145.aspx– It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[2000xp8]

A dyno tune or chip is NOT the solution. It can be one if you want a half assed fix to your problem though.
Whoever told you this is what you need is not the place to take your car anymore, and they probably have limited fox body experience or they are trying to rip you off.

Start with listing your mods, starting with your meter and injectors.

 

[ratio411]

Stock HO long block
Stock injectors 19#

Only mods:
GT40 intake w/1" spacer
Explorer 65mm TB
SN95 MAF (stock 19# calibration)
MAC equal length
2.5" OR-X
2.5" Dynomax bullets
Silencer removed and K&N air filter

All new plugs, wires, cap/rotor, as well as every basic sensor as this is a fresh install.

The car dyno'd 220/270 on the DynoJet.
They were trying to sell us the 'tune'.
I know the car can pull 240 if the AFR was fixed.

We are running the 70mm SN95 MAF. The car was running rich before that, but we didn't know how bad it was. We are going to try the 58mm MAF electronics in the 70mm housing.
That will lean it out. Like I said though, it could be bad if it leans it too much up top.

We tried a scanner on it, but it couldn't 'find' the ECM.
It did the same on my 5.0 pickup truck, so it is probably a scanner problem.

 

[2000xp8]

Stock HO long block
Stock injectors 19#

Only mods:
GT40 intake w/1" spacer
Explorer 65mm TB
SN95 MAF (stock 19# calibration)
MAC equal length
2.5" OR-X
2.5" Dynomax bullets
Silencer removed and K&N air filter

All new plugs, wires, cap/rotor, as well as every basic sensor as this is a fresh install.

The car dyno'd 220/270 on the DynoJet.
They were trying to sell us the 'tune'.
I know the car can pull 240 if the AFR was fixed.

We are running the 70mm SN95 MAF. The car was running rich before that, but we didn't know how bad it was. We are going to try the 58mm MAF electronics in the 70mm housing.
That will lean it out. Like I said though, it could be bad if it leans it too much up top.

We tried a scanner on it, but it couldn't 'find' the ECM.
It did the same on my 5.0 pickup truck, so it is probably a scanner problem.

240 without any heads is pushing it.

Find an old pro m 75mm bullet calibrated for 19's.
They work great and definetely add power. I've seen it tested to gain .2 in the quarter on a stock engine.
Can't see one costing much more than $75-$100 used.
I wouldn't switch sensors then go back to the dyno and blow another $75 on a dyno run.
At your power level and budget, good parts are worth more than just finding out how much power you make.

 

[90stang5speed]

I was looking at your mod list. you have an SN95 MAF but what EEC are you using? Is it from an SN95 car too? the reason I ask is I was looking in EA and the MAF curve for a 96 cobra is diferent than say the A9L EEC that a 90 fox body might have. Im not an expert at this stuff but the curve is richer looking on the low end of things. Also the 96 flow number go higher on the top end. I think if you tried to lean the bottom end out the top end would get dangerously lean. I think WOT is usually around 12.8 on an NA car so you are already starting to lean out up top. If you have the complete MAF from an older fox AND running an older fox EEC, you might try the whole maf & not put the small maf sensor in the big maf housing. hope that helps & good luck. When I had the stock MAF in my 90, it would peg out up top but for some reason, when that happened, it would also be too rich. not sure if pegging out caused the rich condition but, that would be safer than leaning out.

 

[jrichker]

I was looking at your mod list. you have an SN95 MAF but what EEC are you using? Is it from an SN95 car too? the reason I ask is I was looking in EA and the MAF curve for a 96 cobra is diferent than say the A9L EEC that a 90 fox body might have. Im not an expert at this stuff but the curve is richer looking on the low end of things. Also the 96 flow number go higher on the top end. I think if you tried to lean the bottom end out the top end would get dangerously lean. I think WOT is usually around 12.8 on an NA car so you are already starting to lean out up top. If you have the complete MAF from an older fox AND running an older fox EEC, you might try the whole maf & not put the small maf sensor in the big maf housing. hope that helps & good luck. When I had the stock MAF in my 90, it would peg out up top but for some reason, when that happened, it would also be too rich. not sure if pegging out caused the rich condition but, that would be safer than leaning out.

The 94-95 computer won't fit the eariler mass air wiring harness - it has a different number of pins and a different computer connector.
See Ford Fuel Injection » EEC Computers for more information.

The MAF body and sensor are designed to match each other. Therefore you can't swap sensors between different part number MAF bodies and maintain proper calibration. The assembly is designed to match the computer’s internal program, and swapping a different MAF can upset the computer's calibration.

The only other MAF that is a one for one swap for a 93 and earlier 5.0 Mustang is the 94-95 Mustang MAF.

2.) MAF & sensor interchange
The 94-95 Mustang 5.0 MAF & sensor is also found on:
1995-94 Mustang 3.8L F2VF-12B579-A2A,
1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
1994-92 Town Car 4.6L F2VF-12B579-A2A,
1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.

 

[ratio411]

Yeah, it's a 94 5.0 MAF.

The only sensors that are not new are:
MAP (BARO)
MAF
o2 sensors (2)

The o2s are black, but the spark plugs are not.
The Baro is only supposed to tell the computer if you are driving at sea level, or in the mountains.
Correct?

What will bad or poor o2 sensors do?

We swapped in the 58mm guts to the 70mm MAF.
It is still blowing gas smoke out of the exhuast, just not quite as much.
Throttle response 'feels' a touch better throughout. However, the butt-meter is not always accurate.

 

[ratio411]

As for N/A AFR, the dyno guy said to shoot for 12.8:1 to 13.5:1.
He had the benefit of having installed a wideband in the car.

If the o2 sensor was just left hanging on one side during the dyno session, how could the engine run properly? He installed his sensor, and the one for the car was just left out, hooked and hanging by it's wire.

 

[jrichker]

Yeah, it's a 94 5.0 MAF.

The only sensors that are not new are:
MAP (BARO)
MAF
o2 sensors (2)

The o2s are black, but the spark plugs are not.
The Baro is only supposed to tell the computer if you are driving at sea level, or in the mountains.
Correct?

What will bad or poor o2 sensors do?

We swapped in the 58mm guts to the 70mm MAF.
It is still blowing gas smoke out of the exhuast, just not quite as much.
Throttle response 'feels' a touch better throughout. However, the butt-meter is not always accurate.

How badly do you want to fix this car?

You cannot put a 58 MM MAF sensor in a 70 MM housing and expect it to work correctly.

The MAF body and sensor are designed to match each other. Therefore you can't swap sensors between different part number MAF bodies and maintain proper calibration. The assembly is designed to match the computer’s internal program, and swapping a different MAF can upset the computer's calibration.

94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes. *1 *2

Once your replacement 70MM MAF is in place, disconnect the battery for about 10 minutes. When you reconnect the battery and start the engine, the computer will relearn the settings for the new MAF.

*1.) Metal flange adapter Kurtz Kustomz Motorsports, Inc. KKM Buy the TR70 for $44.95. Or spend some time on eBay looking for one that may fit.

*2.) MAF & sensor interchange
The 94-95 Mustang 5.0 MAF & sensor is also found on:
1995-94 Mustang 3.8L F2VF-12B579-A2A,
1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
1994-92 Town Car 4.6L F2VF-12B579-A2A,
1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.


The Baro sensor vents to the open air not to the intake manifold. It measures the current atmospheric pressure. Atmospheric pressure changes with the weather and altitude.


Bad O2 sensors will cause the air/fuel ratio to be incorrect. The typical failure mode is an overly rich mixture. They will cause poor idle, driveablity problems, and poor fuel economy.

Do yourself two favors:
1.) Dump the codes. You may find the defective part or sensor that is the root cause of your problems. My first post tells you how to do it.

2.) Here's a book that will get you started with how the Ford electronic engine control or "computer" works.

Ford Fuel Injection & Electronic Engine Control 1988-1993 by Charles Probst :ISBN 0-8376-0301-3.

It's about $25-$30 from Borders.com see http://www.amazon.com/ . Select boo...very good, and I found it to be very helpful.