1991 Mustang - Idle Problems with no codes

[mr.p]

I had posted in another thread and jrichker suggested I start a new thread for the discussion. I have a 1991 LX Convertible 5.0 that has had an engine swap back to a stock 5.0 (it's a long story but suffice to say there will be an upcoming project). I am having trouble pulling codes using the method posted by jrichker (a method I have used successfully many times in the past and I just used on my 1995 F 150). I have a 1991 LX 5.0 Convertible and I the specific problem that I am having is that it shuts off when I push in the clutch or come to a stop, not always just most of the time. When following the analog meter method to pull codes I get nothing, but I believe something is amiss and here is why. When using this method, http://www.troublecodes.net/Ford/, on my truck I get codes. The difference is that when the analog meter is hooked to my truck it reads 12 volts until the key is turned on and then it drops to 0 to begin the code sweep sequence. On my Mustang, it reads 12 volts when connected but it does not drop to 0 when the key is turned on and never sweeps the needle at all. I then read the thread below that was suggested by jrichker and hopefully we are on to the problem. According to the article:

"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."

While I do have less than 1.5 ohms it practically an open circuit (much less than 1.5 ohms).

See http://forums.stangnet.com/showthread.php?t=608084 for help.

Looking for help.

Thanks

 

[jrichker]

Did you make your measurements with the power off? I recommend that you disconnect the battery positive terminal when making resistance measurements on the computer circuits.

 

[mr.p]

Sorry it has taken so long to respond but when i was coming back up from my shop to get a meter to continue the checks, I completely tore my calf muscle and have been on limited standing time for a while.

Yes, I did make the measurement with the power off although I did not disconnect the battery, I will do that this morning. I think my problem may be related to a ground issue, but I am not sure. I will perform the test on my 1995 F150 to have a benchmark to go against and will post the results shortly.

Thanks for your help

 

[mr.p]

Okay, results time. I disconnected the battery and it reads an open circuit. I performed the same test on my truck following the same procedures and i get a reading around .9 ohms. This leads me to think I have a ground problem (maybe). Is there supposed to be a ground wire for the computer itself? Where should I go from here?

Thanks to all

 

[mr.p]

Step 1: With the power off, measure the resistance
between the computer test ground (black/white wire)
on the self test connector and battery ground cable.
You should see less than 1.5 ohms.

Results: I have no resistance what so ever (meter reads OL with no beep indicating a closed circuit).

Step 2: If that checks good, 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 STI computer self test
connector (red/white wire) and pin 48 on the
computer main connector.

Results: The resistance reads approximately .8 ohms.

While I have the connector off of the computer,
I decided to measure the resistance between the
computer test ground on the self test connector
and pin 46 on the on the computer connector and
I have about 1.1 ohms. This makes me wonder why
I receive no reading when the connector is
connected to the computer.

So, if I have no resistance reading in Step 1 and approximately .8 ohms resistance in Step 2, what now?

Thanks

 

[mr.p]

Okay, just for grins, I had the parts store give me a new computer and I still have the same results. Please, someone help.

Thanks

 

[fidstang]

There is a switch that make sure the clutch is engaged in order to start the engine mine for some reason had a bad connection and was causing it to not start and every great once in while stop the engine when stopping suddenly. Other then that how is your relay to the pump and inertia switch?

 

[DEADWOOD]

... when i was coming back up from my shop to get a meter to continue the checks, I completely tore my calf muscle...

Jeez, how the hell did you do that?