different engine wiring

[I'll sho u]

I am about to do a engine swap on my 94 mtx sho.The donor engine is really low milage,about 55k,but is out of a 90 mtx sho.Is there any difference in the engine wiring harnesses between the two.I don't really feal like taking the fuel rails off to remove the wires under them.I am hoping that they are interchangable.

 

[rangerj]

Keep in mind that 1994 was a year of changes.

See the wiring diagrams posted and compare the engine compartment wiring for the 90 and the 94. Compare each and every wire attached to the engine.

Next, make a list of the sensors and any other components, eg the IAB, EGR. Then go online to a parts place, like Rock Auto.com, and look up each sensor and component for the 90 and the 94. Any sensor that has a different part number should be changed to the 94 part.

Compare each and every connector. Any connectors that are different have to be changed to the 94. DO NOT cut and splice the wires. Remove the pins, one at a time, and insert them into the 94 connectors. The pins, and/or spades, have a tang that holds them in the connector. If there are any major differences you will have to change over to the 94. I do not think there are any major differences, but I have not done this myself on a SHO.

The tang can be pushed on with a paper clip end and the pin will slide out, (and snap back in). Remember, do one wire at a time and keep the wires matched to the other end of the connector. You may not have to change any connectors, but if you do you will know how.

The idea is to have everthing matched to the 94 computer. The engine itself will not know the difference. If you do not do your homework on this kind of swap you could be spending a whole lot of time trying to get things to work right later. This sounds like a good learning project. rangerj

 

[HighSpeed]

What makes the '94 mtx different from a '92 or even a '93 mtx engine wise electrically? The '92 and later mtxs all used the X2J computer.

?

 

[rangerj]

Highspeed,

You are correct the 92, 93, and 94 use the same computer and the perameters of the sensors should be the same for those model years. However he is installing a 1990 engine and the perameters of the sensors MAY be different. So I suggested that he check the sensors for any differences rather than assume that they are the same.

The easiest way to do this is to compare part numbers, for example if the same part number sensor will work in 89 through 1995, you know it is OK to use that sensor in the swapped engine.

I do not know of anyone outside of Ford that has an exact list of the differences between the 1990 and 1994 model years. That is why I suggested that he also compare the wiring diagrams.

If a 94 connector has 5 wires and the 90 connector has 4 wires, there is an obvious need to find out what the additional wire is for. We do not know if this example situation will occur, but that is the problem, that is we do not know! The solution I recommend is to find out now, not later. rangerj

 

[I'll sho u]

I swapped engines on this past saturday with no problems,found that all the sensors were the same but the engine harnesses were different.They had the same wires but the connections where the engine harness plugs to the main harness were of different style and would not plug tougether

 

[SHO--ripper]

For future reference you use the main harness from the car the motor is going in, and you can keep the injector harness on the motor.
Glad to hear the swap went smoothly