Hello friends! I am completely stumped here and I am hoping you all can help. My nephew had a project going that fell into my lap, unfortunately and I have a general knowledge of cars, motor swaps of this nature I am unfamiliar with. He started with a 1996 Mustang with the 3.8 V6. The motor locked up, (due to him busting out the oil pan). He bought a 1994 Mustang with the 3.8, thing ran great, just had no title. He had someone put the motor from the 1994, into the 1996. From what I can see they put the main harness and the ECM from the 1994 into the 1996 along with the motor. Motor is getting fuel, 38psi on the gauge. I pulled a spark plug with the wire still on it and I see it arcing. It’s just cranking, not even thinking about firing. I know it is most likely something simple. I guess my main question here is, since a 1996 motor is being replaced with a 1994 motor, what else has to be moved over to the 1996 besides the main harness and ECM? Any and all input is very much appreciated, hoping I didn’t get myself into anything too crazy here. Thank you all and have a blessed day!

 

Welcome to the forums!

Now, not an expert, buuuttt... 3.8 is a 3.8, ostensibly, in this case. Long block wise anyway. That's the main block, pistons, rods, crank, oil pump, oil pan, heads, camshafts, chains. And stop. From there on, things can be different.

I hope you have the old engine to obtain the parts from, as what you'd do is simply strip anything that's not above from that old engine and put it on the new one. Intake, water pump, hoses, electronics, harness, etc, ad nauseam. Everything that is on the old block needs to be on the new long block. *Everything*. If someone didn't push a part from the old engine to the new one, well, that'd be a good guess as to why it's not running.

One other gotcha: There may be a running change from '94 to '96 that also may make this swap invalid. Something small like where the crankshaft position sensor is, or something of that kind of esoteric nature. Little details can make a big difference, and it may be that a '94 3.8 is not set up the same as the '96... unless it's in a part that *can* be swapped, like a timing cover might swap from the 96 to the 94 engine and voila, now it's compatible with the 96 ECU. It's *supposed* to be the same, near as I can tell, but automakers frequently do little things that are annoying like this, so you gotta compare the two closely to be sure.

If it's too much, you might pay a good mechanic who's done such things to take this over. Parts is parts, truth, but if you don't know, you don't know. Gotta learn or gotta let someone else do it, that's the options.

Hope it helps, good luck!

 

This is incredibly helpful! Thank you. I do still have the old engine and nothing was moved over from the engine as far as sensors and intake and such. The only things that were moved from the donor car was the motor itself, the harness and the computer along with some sort of module in the passenger side fender area. Since I am putting parts off the original engine onto the 1994 engine that is now in the car, does that mean the 1996 harness and computer have to go back in? Thank you for all the help!

 

Quote:

The only things that were moved from the donor car was the motor itself, the harness and the computer along with some sort of module in the passenger side fender area.

This is why the car isn't running (ostensibly). Remember, I'm wayyy over here...

Since the only thing wrong with the 96 was the oil running out and then locking the motor up, the long block itself is the only 'part' needing to be replaced. All other things including the harness, computer and whatever modules would have stayed in the 96, and the otherwise stripped 94 long block would have been put in and all that stuff connected to it.

That someone decided to swap out the harness and computer... well, it's a thought process, truth. But the car's PATS wouldn't like it and that's why the car's not running (GUESS on my part, not for sure.) You'd have to reprogram the PATS to the computer to get it to work.. Possibly. Not sure about that, but computers do get swapped... but not backwards, typically, as in this case being a 96 going to a 94 computer.

In this case, though, it'd be easier to put it all back to 96 and avoid any more oddities. The car was otherwise fine, no need to complicate it further than the long block.



...and it still may not work, because you don't know what's all been done besides this. It could be that they tried to reprogram, have different keys, etc, ad nauseam and this is a lost cause now. You might just want to consider other options like... parting them out, or if you must get this running, go get a Holley Dominator to run the thing... IDK, but it's getting to a point already of costs vs payoff now...

But I believe in you! Just don't get caught up in a money and time pit is all, k?