Mass Air Meter Size

Ok. orange injectors are 19lbs. GT40 heads have either 3 or 4 bars( gt40P) on the front and back sides of the heads.

What do you mean by the right MAF- do you mean diameter or injector? Is it a Ford or aftermarket unit? If Ford. post the part number on top of it. The MAF is matched to the computer not the injectors with a Ford MAF. Most 5.0 mustangs except for the Cobra have a EEC that is for 19lb injectors and MAF. The Cobra is matched to 24lbers.

Are you having driveability problems? If so, run the codes. You' ve pulled a bunch of smog equipment off and are probably causing the EEC to have fits.

Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't 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.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10




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 www.midwayautosupply.com/Equus-Digital-Ford-Code-Reader/dp/B000EW0KHW Equus - Digital Ford Code Reader (3145It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.

49 shoebox said:

I'm trying to make sure I have the right mass air meter for my injectors. What I have is a 1987 5.0 HO with GT 40 heads ( I think.... Have long spark plugs) mass air conversion ( bought off ebay years ago see pict) custom harness ( Windsor fox) No smog pump, unplugged EGR valve, no Ac, no power steering,headers, MSD coil and wires, I have orange injectors if that helps.

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I'd like a picture of how your Serp belt is routed with only an alt, crank and WP and some sort of belt tensioning device.

FoxMustangLvr said:

I'd like a picture of how your Serp belt is routed with only an alt, crank and WP and some sort of belt tensioning device.

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What does that have to do with his meter size??
As long as the meter is matched to the flow rate of the injectors, the stock one, the sn95 junkyard upgrade or a BBK 73 mm will all work. The last two will flow better, but unless the throttle body and EGR or spacer plate is also upgraded, and the intake mouth is the right size, do not expect a big jump in power.

7991LXnSHO said:

What does that have to do with his meter size??

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Absolutely nothing to do with it. It's a simple request for a picture of his serp belt.

Thanks for the pic of the serp belt. I've never seen the tension arm setup like that.

One thing I see that I believe is hurting you is your MAF and filter is mounted directly onto your throttle body. You want some distance between the MAF and TB so you'll need to get an intake pipe and mount the MAF more upstream. I also believe the air filter should not be mounted directly onto your MAF as this could result in turbulent air.

@jrichker for your codes and how to repair.

Also pull the plugs for the cylinders that are reading cooler than the others. You may have a faulty injector, bad plug or bad plug wires. Start the car in the dark and look for arcing wires.

Sweet car!!!

49 shoebox said:

I bought a digital code reader, I got these codes:31,81,82,85,84, still trying to read up on how to dump these with the reader. What is the air diverter ( code 82) I am thinking this might be the problem. Since all the others are EGR related (I think) thanks everyone has been very helpfull!

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All your codes are emissions related. Since the car is a 49, I would not worry about them. To the best of my knowledge, there is nothing that will affect the car's performance in your case. You may lose a little bit of the fuel economy, but it shouldn't be a serious problem

The one thing I would try to do is to locate the MAF and air filter in some place that can pick up cool, non- turbulent air. The Fox body Mustangs pick it up from the inner fenderwell. Some PVC pipe from Home Depot, Lowes or ACE Hardware may help you to fabricate a more suitable cold air intake system.

GT40 head identification, 3 bars = GT40, 4 bars = GT40p

Just look up a BBK cold air intake for a mustang 5.0 and that should give you an idea. There are special MAF's out there that you can directly mount a filter to, I think ProM makes them and their called a Bullet.

Also, the MAF is calibrated for a specific injector size only. A MAF for 19# injectors will not work well with 24# injectors. You will have idling and drivability problems if you mix and match. Your motor should be good with 19's