Engine 95 5.0 Still Running Like S#@!, Many New Parts Installed, Stumped?????

Dash mode?
Do you mean counting the flashes of the check engine light?

I would buy a code reader from walmart or orileys.
They are around $40 and much easier then counting flashes.

Get the codes and report back.

Did you remove the spout connector when attempting to set timing?

The only other thing I can think to check if your timing light doesn't seem to match what's happening in the distributor is the condition of the harmonic balancer. Those have been known to come apart / shift (check for any protruding rubber behind it). You mentioned the timing chain is solid so I wouldn't think you jumped a tooth or two but it might not hurt to crank it over with the distributor cap removed so you can see if the rotor is moving smoothly and consistently around the circle. Then of course you could have a PIP/TFI problem as well or just general engine ground issue.

Aside from a timing issue, you could also be running rich for some other reason, but probably important to get the timing sorted first. Then it's on to codes. Did you move the injectors over from your old engine as well?

Computer will not go into diagnostic mode on 91-95 model 5.0 Mustangs

How it is supposed to work:
The grey/red 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 grey/red 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. Only an experienced electronics technician can open the computer up & repair the trace if it burns up and creates an open circuit.

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 (grey/red 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 grey/red 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 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 grey/red wire goes. Almost every sensor on the engine except the MAF is connected to it.


Complete computer, actuator & sensor wiring diagram for 94-95 Mass Air Mustangs


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.

israela said:

@jrichker I think you might be right about the ecm on this one. After reading your post I began to search around and found a post over at allfordmustangs where this guy describes all my symptoms like my cooling fan coming on at start up, whining fuel pump, rough idle, not being able to pull codes and a new ecm fixed all the issues after he bought all new parts. Sounds familiar???

Click to expand...

Not being able to pull codes is definitely a sign of trouble. See my previous post in order to correctly diagnose the problem.

israela said:

@jozsefsz Do I need to turn the crank over twice for the rotor to complete a full turn??? Sorry for my lack of knowledge on 5.0 distributors lol, am used to coil packs

Click to expand...

Yes you're correct, twice around the crank gives you once around the distributor. I'm siding with you both on the potential for computer problems, though agreed with jrichker I'd go through the whole procedure before making that guess (unless you had a spare computer laying around already).

An OBDI reader can be had for about $22. See here [url="http://. One of the least expensive items in the tool box that you shouldn't be without"]. One of the least expensive items in the tool box that you shouldn't be without.[/url]