Fox Feels Slow.

What year is your car?
Is it Speed Density or Mass Air?

Basic questions:
1.) Is there fresh gasoline in the tank? Gasoline loses some of the qualities that make for good performance if it is more than 90 days old. The blend of products that make pump gasoline changes with the seasons.
2.) have you changed the fuel, oil and air filters? If not, why not?
3..) Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

4.) Figuring out rear axle gear ratio:
Don't bother with removing the cover from the rear axle. It is a stinky, messy job and you need the connect lubricant combination to refill it when you are done. There is a much simpler way to do it.
The rear end gear question is very simple to solve.
1.) Jack the car, up so that the rear wheels are off the ground. Be sure to use jackstands under the body mount for the lower rear control arms for safety's sake. With the jackstands supporting the body, the rear axle will drop so that it will be easier to see and count the number of turns the driveshaft makes.
2.) Make a chalk or paint mark on the driveshaft so that it is easy to see.
3.) Make a chalk or paint mark on the tire.
4.) Turn the tire one full turn while counting the turns make by the driveshaft.

302 GT40 heads 373 rear T5. Tuned right with sticky tires and a competent driver should net mid to low 13's. Do you consider that fast, or slow?

Check your ignition timing and set it at 12 to 14 degrees initial and see if that wakes it up.

Before I put my blower on when everything was basically stock, it was somewhat sluggish. Then I cranked the timing up and it started spinning wheels and chirpin some serious gears. But you get used to it pretty quick and need more......and the story continues.

In the end, I'd rather have a sluggish Foxbody than a peppy Hundai.

That veloster has 201hp and is lighter than the about 225hp fox... What cam is in it ? Some cams don't open up till later in rpm. I've seen "built" mustangs put out 213 rear wheel HP on a Dyno. If the combo isn't right it can hurt horsepower.

We just don't have enough info to really help you. What intake, cam, injectors, CAI, MAF, upper/ lower intake, throttle body, exhaust, and tune ? It could be as simple as the timing not being set right. Go through what jrichker posted and give us more info.

Definitely start by checking your timing. If it's running less than 10 degrees btdc, it's going to be a total turd. You'll prob want it somewhere around 14-15 degrees with that setup.

check your plugs, rotor, cap, timing, etc basic stuff. Any vacuum leaks? TB and MAF clean? As mentioned, a well tuned car with that setup is an easy low 13 second car.

jrichker asked the most important question so far;

What year is your car?
Is it Speed Density or Mass Air?

If its Mass Air and still has the stock 55mm MAF, theres a significant bottleneck. Mine fell flat at about 4800rpm on the 55mm maf. When I swapped in the 70mm Marquis maf, it screamed to 6000 and beyond.

Southport2014 said:

Thanks everyonebfor replies. now thr car is acting up. its bucking and jerking after warmed up

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Pull the codes, takes less than five minutes and a paper clip. Also, if possible verify your timing.

Furthermore, what computer is the car running A9L, A3M, or the DA1?

Lastly comparing a turbo four cylinder with almost 30 years of advances in technology to a tired 2V V8 isn't really a fair comparison IMO.

Southport2014 said:

All i have done to car since first post was drive it. Its a 5 speed. Idk if it was a manuel before. I have to check rear end still. Heads is there a easy way to check. ? Its a a9l computer. I will be pulling codes when i get home.

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The driver side door sticker should have a TR code on it. Should be either a 2 or W for a Manual.

Grab the Axle code too or maybe take pic of it.

Also it sounds like it has 2:73s instead of 3:73s at 55mph on the highway what's your RPM....like 1500, 1800, 2200?

Heads have stampings on them lower right corner usually or grab some pics

Southport2014 said:

Well went and tried to pull codes and no luck.

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Computer will not go into diagnostic mode on 86-90 model 5.0 Mustangs

Disconnect the battery positive terminal before making any resistance checks.
The voltage drop in the ground cable will cause incorrect resistance readings.

How it is supposed to work:
The black/white wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self test mode. If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. Since it is a dedicated ground, it passes through the computer on its way to the computer main power ground that terminates at the battery pigtail ground. It should read less than 1.5 ohms when measured from anyplace on the engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.

What sometimes happens is that the test connector black/white wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.

The STI (Self Test Input ) is jumpered to ground to put the computer into test mode. Jumpering it to power can produce unknown results, including damage to the computer. The ohm test simply verifies that there are no breaks in the wiring between the test connector and the computer input.

How to test the wiring :
With the power off, measure the resistance between the computer test ground (black/white wire) on the self test connector and battery ground. You should see less than 1.5 ohms.



If that check fails, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the black/white wire and pin 46 on the computer wiring connector: it should be less than 1.5 ohms. More that 1.5 ohms is a wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1.5 ohms. More that that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.

See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.

If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More that 1.5 ohms is a wiring problem

The following is a view from the computer side of the computer wiring connector: it is for an A9L, A9P computer.




Diagram courtesy of Tmoss & Stang&2birds

Check out the diagram and notice all the places the black/white wire goes. Almost every sensor on the engine except the MAF is connected to it.



See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine

See the graphic for the 10 pin connector circuit layout.