96 98 swap issue

[straightpaint]

So I swapped a 98 motor and trans into my 96 with the matching Ecu. Car wouldn't run. But runs with my 96 ecu. Unfortunately doesn't seem to be running 100% on that tune. Keeps flashing theft on the dash and cuts out the fuel. What's the fix for this? Is the problem the chip in the key?

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[Mkbrower]

So I swapped a 98 motor and trans into my 96 with the matching Ecu. Car wouldn't run. But runs with my 96 ecu. Unfortunately doesn't seem to be running 100% on that tune. Keeps flashing theft on the dash and cuts out the fuel. What's the fix for this? Is the problem the chip in the key?

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The wiring is different from 97 to 98. Best to use the 96 engine harness and 96 ECU. There is a pressure transducer used in the 98 fuel tank and a vapor management valve that the 98 ecm will look for and will probable throw a CEL when it doesn't find it. The engine harness is pinned a little different for some sensors on the 98 harness that will not match on the 96 ECM engine harness plug C-104.

 

[straightpaint]

No CEL as of yet. Is it pined different at the ecu or at the firewall on the motor harness?

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[Mkbrower]

its a matter of time on CEL but it will show up. The ECM 104 pin connector is pretty much the same with the exceptions on the previous post. The difference is the engine harness plug near the fire wall in the engine compartment. Here are some of the difference:

EVAP purge flow valve comes off pin #2 in 97, pin #27 in 98
RF O2 sensor comes off pin#20 in 97, pin#3 in 98
Pin #20 on 98 engine harness goes to fuel injector #7 and may explain why your engine feels like its missing.

There are more differences and what I listed is only a sample. It makes using the 98 engine harness with the 96 ECM harness more difficult than just using the 96 harness on the 98 engine.

The 98 ECM may not work due to PATS. Not sure, but I believe the 96 mustang didn't use PATS or it works differently. Either way, the 98 ECM will need to be programmed to work with the 96 PATS security system or get turned off by a tune. This is why its probably best to use the 96 ECM.

Mark

 

[Mkbrower]

I apologize but I may have given you some bad information. I was looking at the pin-out for a 4.6 2V and not the 4.6 4V. I actually have a 97 cobra engine harness that I was comparing and they are a lot closer but still different. Most major engine components look the same though. Ill do a little more research and let you know all the differences between the 97 ECM harness and the 98 engine harness.

 

[straightpaint]

Ok i appreciate it. Im wondering if i should hunt down a 98 ecu harness to meet the 98 engine harness. Found one for $250. But im wondering if it would help any. I just dont want to cut any corners. If theirs a chance that injector 7 pin goes somewhere else i cant risk that. If its a matter of cutting and splicing a few wires im not scared lol. Ford is telling me to bring it to them let them program me 2 keys and reprogram the 98 ecu to make it work. But how if the motor harness and the ecu harness dont match 100% That is the million dollar question. Once solved im making a set of plug and play harness's so no one has to go through this again.

 

[Mkbrower]

I don't think the 98 ECM harness will help you much. Not much different than what you have with the exception of the extra fuel tank sensor connectors.

 

[Mkbrower]

I'm still trying to verify the actual engine harness as I have found some descrepencies in the service manual.

 

[straightpaint]

I just figured if it matches the ecu and the engine harness plug 100% how could it not help. I mean if not that's 250 bucks I could invest into something else.

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[Mkbrower]

the dash harness also plugs into the ECM harness and I know there is a electrical difference between the 98 and 97 instrument cluster. Ive read its just a couple of wires but not sure which ones and what is affected

 

[straightpaint]

What should I do lol.

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[Mkbrower]

i am doing the same as you except I'm trying to use a 98 4.6 2V ECM harness with a 97 4V engine harness and engine and controlling it with a 98 2V ECM. My car is a 98 base V6. Ive been trying to keep everything 98 cause the car has to pass OBD2 emissions and has to be the same year or newer.

The problem I'm running into is 98 electrical harness is different from 97 and 99 so it was only available that one year and as you are aware is expensive and hard to find. especially the 98 4V engine harness.

I have all the electrical diagrams for 97 and 98 and it seems ford couldn't keep the electrical diagrams straight, as I keep finding discrepancies. There are a few differences but all the engine controls appear to be the same in 97 and 98 unless you are trying to use a 2V engine harness. Remember, the 98 mustang use a fuel tank pressure sensor and the 98 ECM will look for it and tank level to calculate what pressure should be. Will probably throw a CEL light unless you have those inputs programmed out of your ECM.

If I find anything different Ill let you know but as of now, I think you are good on your harnesses.

 

[straightpaint]

I have the 98 engine harness that came with my motor and the ecu for it too. I just need the dash harness.

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[straightpaint]

Anyway I could get those diagrams from ya? 97 should be the same as 96 which is what my base is [96 4v] so diagrams for 97 and 98 should help

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[straightpaint]

came across this

 

[straightpaint]

Well just finished taking the dash out. So I guess I need the dash harness and ecu harness now and a gauge cluster for a 98

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[straightpaint]

So at this point I've changed the dash harness and ECU harness to match my 98 motor and 98 motor harness car still a 96 I've tried both 96 and 98 ecu's. You can still not get the car to run I've also put in a set of 98 gauges. The car will idle for about 2 seconds and stall using the 96 ECU and will not idle at all or start on the 98 ECU. What do we think The Next Step Maybe

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