Need Help 94 5.0

You NEED..... Hold on let me repeat that, NEED o2 sensors. Unless you have been tuned to eliminate them your car well run in limp mode and have all sorts of driveability issues like the ones mentioned.

When was the last time you cleaned and oiled your filter?

I'm with styk. Unless you have a standalone aftermarket fuel management computer, you must run O2 sensors. The only exception here is if the car has been converted to a carbed setup. I would jack the car up and have a second look for those O2s.. maybe you overlooked them? If they aren't there, look for the harness connectors for them and look into adding them to the existing exhaust. They are a necessity. Have you checked to see if the car is throwing any codes?

Without going through the surging idle checklist which I strongly urge you to do, clean your maf. Filter oil is horrible about gumming up the screen. Then take another look for those o2s.I've seen them tucked up on top of pipes where they still get enough temp reading to quasi function.

Agreed again. They have to be there somewhere. Most likely in the H or X pipe.

Maybe @jrichker can help you with one of his fantastic checklists...

Jacob302 said:

Straight pipe to flow master

Click to expand...

Well, whatever the setup.. go over it again. Run your hands along the top of the pipes like stykthyn said. I'd wager they are there and finally crapped out. If they aren't there, the car has been in limp mode and finally gave up.. and you'll need to add the O2s, clear codes and go from there.

Either your car has been hacked together or you've had tuning that need to be disclosed. Either way here is the place to start.
Help me create the "Surging Idle Checklist" | Mustang Forums at StangNet

Before spending another dime go through the list. 99.9999999% of the time the answer is on there.

02 fittings are on the mid pipe not the headers

You don't need a shop full of fancy equipment to dump the codes, at you need is a 5 cent paper clip...


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 Equus Digital Ford Code Reader (3145) 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 $22-$36.