[sisch]

We're on our last legs of getting my [censor] 1994 3.8 converted to a 5.0. We've changed just about everything on the 5.0 engine including heads (lo and behold they were cracked!), all lifters, distributor pickup coil, well you name it and we've probably replaced it with the exception of the block and intake manifold.

Anyway, we've hit a hicup that we just can't seem to get over. Until today. But it's still a problem. So once again I turn to the masters of modding mustangs to hopefully solve our problem.

With everything connected "properly" when we test drive the car it WILL move, but it has "issues". When we push on the accelerator too much it stumbles and almost but not quite falls flat on her face. However, once it gets into 3rd gear it's okay. So my friend decided to try unplugging the part of the wiring harness that connects to the transmission. Surprise surprise it runs "correctly" (in "limp home mode" of course). When the harness was first disconnected, it was like the car had gone from being 'in gear' to park, from the way the engine sounded.

Our question is this... is the transmission wiring harness different between a 3.8 and a 5.0? The only other option is that maybe something on my current harness got messed up.

Any input we could get at this point would be VERY much appreciated. Once this particular problem is solved I can FINALLY inspect and register my car after waiting 6 years to do so.

Thanks,
Sisch

[93hatch]

whats the timing at?

[sisch]

Timing is set at 10 degrees BTDC

It's not the timing, trust me. Without the transmission harness plugged in, the motor purrs like a kitten, and runs great. Plug the transmission in, and it's like it's immediately put into gear, and gets worse when you ACTUALLY put it in gear.

[93hatch]

Idk shit bout autos lulz. Free bump

[jjpluml]

are you running the 3.8 tranny or the 5.0?

[sisch]

Its the 4R70W form the 3.8 and the wiring wiring harness for it is from the 3.8. The engine harness and computer are from a 5.0 everything else is from MY 3.8 which was working just fine prior to the conversion.

[jjpluml]

id bet the harness is different on a 5.0... havent ever used the 3.8 tranny behind one so i cant say for sure. Ill try and take some pics of one off a 5.0 tranny tonight and post them up so u can look and see if they are different. Id imagine since your running a 5.0 computer and that tranny its getting confused somewhere. Try pulling the relay out of the harness that connects to the distributor with the tranny plugged in and see if it changes anything. If it does youll know that the computer is having problems compensating for the different tranny

[sisch]

Turns out that it was the pin configuration. Three pins on the 3.8 transmission harness are out of place when trying to connect it to the 5.0 ECU harness. I will post later what they are as soon as I can make the changes something that someone other than me can understand. It's currently in "Sisch Shorthand". As soon as I translate it to English I'll post it.

Thanks to all that have helped with this conversion. She's now ready for inspection and registration after a couple tweeks the most prominant being gluing the rearview mirror back onto the windshield.

Sisch

[ryanw]

So are you going to get a different harness or switch some wires around ?

[sisch]

We modified the existing 3.8 harness by removing the O2 sensors that weren't needed and correcting the pinout to match up with the 5.0 ECU harness. Again, when I get the chance, I will translate and post the pin out changes that need to be made.