HELP! Bought a 2004 4.6L Swapped mustang

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Petericaza

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Dec 3, 2019
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The video definitely loads for me. Check this:
How to turn off restricted mode for Youtube.
I used a test light on the injectors it stayed light it didn’t blink or rapid flash like in the video but it stayed lit. I also put a screw driver on each injector and they clicked rapidly and did not sound different so im assuming the injectors are good. I also flushed the steering line and added more in but the sound is just as loud.
 

tsemmett

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Jul 2, 2019
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One side of the injectors will stay lit (it's connected directly to the battery power), across both pins it should flash. But, if you're hearing all 8 injectors clicking, they should be firing.

How well does it run? Pretty smooth, or does it seem like it has a miss?
 

Petericaza

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Dec 3, 2019
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One side of the injectors will stay lit (it's connected directly to the battery power), across both pins it should flash. But, if you're hearing all 8 injectors clicking, they should be firing.

How well does it run? Pretty smooth, or does it seem like it has a miss?
It runs pretty good not sure if I can send videos but it does seem like anything’s wrong at all.
 

tsemmett

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Jul 2, 2019
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I would think a short in the actual wiring would cause the injector to fail to fire, and cause the engine to run poorly. Do you have access to another 4.6 PCM (you mentioned a 2004 car for parts)? I'd be curious to see if another PCM does this, but that can also create its own headaches.
 

Petericaza

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Dec 3, 2019
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I would think a short in the actual wiring would cause the injector to fail to fire, and cause the engine to run poorly. Do you have access to another 4.6 PCM (you mentioned a 2004 car for parts)? I'd be curious to see if another PCM does this, but that can also create its own headaches.
Oh no it’s a 99 gt engine in a 2004 I don’t have an extra pcm at the moment I can check autozone but I think it’s a strange problem because the car runs fine to my knowledge
 

tsemmett

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I misread that then. The reason I ask is that if the injector is firing, the wiring should be good. Now that it's confirmed, it may make sense to replace the PCM. Autozone won't carry a PCM in stock, if they carry one at all. Probably gonna have to look in Mustang classifieds or eBay.
 

Petericaza

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Dec 3, 2019
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I misread that then. The reason I ask is that if the injector is firing, the wiring should be good. Now that it's confirmed, it may make sense to replace the PCM. Autozone won't carry a PCM in stock, if they carry one at all. Probably gonna have to look in Mustang classifieds or eBay.
Alright will that pcm be the reason why the ses lights Is on and the ignition coil code too as well as my speedometer not working?
 

tsemmett

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The PCM (Powertrain Control Module) is what throws those codes and triggers that light. In that year, it also controls the gauge cluster. But, given that your car has been heavily modified, I can only say maybe... There's no way for me to know what the previous owner did in the swap, and it's possible the wiring you're dealing with is non-standard. If you can find a PCM for a reasonable price, it wouldn't be the worst idea to swap in; I would not be surprised if that resolves the issues.
 

Petericaza

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The PCM (Powertrain Control Module) is what throws those codes and triggers that light. In that year, it also controls the gauge cluster. But, given that your car has been heavily modified, I can only say maybe... There's no way for me to know what the previous owner did in the swap, and it's possible the wiring you're dealing with is non-standard. If you can find a PCM for a reasonable price, it wouldn't be the worst idea to swap in; I would not be surprised if that resolves the issues.
Alright I found one but should it be for my year engine 1999 or should I get a 2004 or? Also the previous owner told be that the light came on after his mechanic put the valve cover back on. He also cracked the cover
 

wmburns

SN Certified Technician
Aug 14, 2009
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I found one but should it be for my year engine 1999 or should I get a 2004 or?
The model year of the PCM should be chosen based upon the body wiring harness used during original swap. Remember that the PCM and wiring need to work together as a system.

For example if a PCM from a 2001+ PCM were mated to a body wiring harness of a 1999-2000 MY then the AC clutch will not engage.
 
Last edited:

Petericaza

Member
Dec 3, 2019
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San jose
The model year of the PCM should be chosen based upon the body wiring harness used during original swap. Remember that the PCM and wiring need to work together as a system.

For example if a PCM from a 2001+ PCM were mated to a body wiring harness of a 1999-2000 MY then the AC clutch will not engage.
So since I have a 1999 engine I should get a 99 body wiring harness? Or should I get a 2002 harness to match the pcm ?
 

wmburns

SN Certified Technician
Aug 14, 2009
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So since I have a 1999 engine I should get a 99 body wiring harness?
The model year of the motor itself has little to do with this. Virtually the SAME motor is in the entire model year range from 1999-2004.

Or should I get a 2002 harness to match the pcm ?
I don't think that you appreciate what is involved with wholesale changing of a car body's wiring harness. It's not something done just because you "think" it might magically "fix" any of the problems you are having.

Part of the problem here is IMO you are not fully aware of what parts have or haven't been swapped as part of the V6 to GT swap.

To me it makes the most sense that the LEAST number of parts were swapped to make it run. So in that light, you should 'assume" the body wiring harness is of the ORIGINAL car's model year (2004) until you find out otherwise.

In terms of interchangeable there are little wiring differences within the 2001-2004 model year range. So one of the worst things you could swap is across the 1999-2000 model year range to the 2001-2004 model year range.
 

Petericaza

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Dec 3, 2019
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So what would you reccomend I do the car has a 99gt in it an unknown t45 transmission and a 2002 computer the I want to know what I can do to get the speedo working. The car runs and sounds fine except when the ac is on the it makes a clicking sound at intervals I just want the car ready so I can smog it and legally drive it
 

wmburns

SN Certified Technician
Aug 14, 2009
5,893
521
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Houston Texas
I have already given you a ton of information. Can't go further until some key diagnostic information is provided by yourself.


IMO it would be best to keep the information about trouble shooting the speedometer problem in the speedometer thread. Otherwise it will be impossible to follow what has and hasn't been done.

The last update that I'm aware of is that the PCM reported speed is very low. This would indicate either a PCM programming issue or a problem between the PCM and the transmission speed sensor.

 

Petericaza

Member
Dec 3, 2019
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San jose
I have already given you a ton of information. Can't go further until some key diagnostic information is provided by yourself.


IMO it would be best to keep the information about trouble shooting the speedometer problem in the speedometer thread. Otherwise it will be impossible to follow what has and hasn't been done.

The last update that I'm aware of is that the PCM reported speed is very low. This would indicate either a PCM programming issue or a problem between the PCM and the transmission speed sensor.

 

Petericaza

Member
Dec 3, 2019
66
2
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San jose
Here this will help you a lot I’m assuming I took out the speed sensor and here’s what i got I also found the tranny tag
 

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