HELP! Bought a 2004 4.6L Swapped mustang

Petericaza

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Dec 3, 2019
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I bought a mustang”gt” it was listed however I went to see it and realized it was a base 2004 with a 4.6l swapped engine and tranny with it I bought it anyway but now I’m trying to figure out why there’s so many codes regarding open circuits in cylinders as well as when I press the break or turn the wheel there’s a loud ass buzz sound to it. He did say it needed a new computer not sure what he means I could use help I’m a lost soul at the moment
 

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wmburns

SN Certified Technician
Aug 14, 2009
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Houston Texas
Start with the basics. Power(s) and ground. Confirm key on +12 volts at injector #2 and #5. Best to use a test light that will "load" the circuit.

Use a "noid" light to confirm the firing pulse on each of the injectors.
 

Petericaza

Member
Dec 3, 2019
66
2
8
48
San jose
Start with the basics. Power(s) and ground. Confirm key on +12 volts at injector #2 and #5. Best to use a test light that will "load" the circuit.

Use a "noid" light to confirm the firing pulse on each of the injectors.
I don’t have a test light I can buy one and when I do do I touch it to the injector itself and see if it’s putting out 12 volts for each? Like I said the guy before me swapped the engine and transmission it was originally a v6
 

wmburns

SN Certified Technician
Aug 14, 2009
5,842
505
194
Houston Texas
Just wondering. Has this motor ever run?

Soooooooooooooo. Does this car still have a V6 PCM? IF so, this is your problem. There's is no way a V6 PCM can run a V8. The V6 PCM does not have the correct number of COP drivers. The ignition system is totally different (waste spark verses COP).

Remember that the wring and the PCM have to work together as a SYSTEM. Incorrectly mixed and matched parts will likely not play well together.

For a correctly working motor there is a key on constant 12 volts at each injector. The test light is use to confirm this.

The "noid" tester is used to confirm that each injector is actually receiving the grounding "pulse" to fire.

Note, the DTC means either:
  • there's no power at the injector.
  • the injector coil is open
  • the signal return line is open.
  • the PCM's injector driver circuit is BAD.
Here's some more information that may be of help to you. Especially if considering swapping the PCM.

ForScan ODB2 scanner w ELM327 USB
 
Last edited:

Petericaza

Member
Dec 3, 2019
66
2
8
48
San jose
Just wondering. Has this motor ever run?

Soooooooooooooo. Does this car still have a V6 PCM? IF so, this is your problem. There's is no way a V6 PCM can run a V8. The V6 PCM does not have the correct number of COP drivers. The ignition system is totally different (waste spark verses COP).

Remember that the wring and the PCM have to work together as a SYSTEM. Incorrectly mixed and matched parts will likely not play well together.

For a correctly working motor there is a key on constant 12 volts at each injector. The test light is use to confirm this.

The "noid" tester is used to confirm that each injector is actually receiving the grounding "pulse" to fire.

Note, the DTC means either:
  • there's no power at the injector.
  • the injector coil is open
  • the signal return line is open.
  • the PCM's injector driver circuit is BAD.
Yes it runs it sounds fine to me I cleared the codes and all that but the guy I bought it from told me it needs a new computer for it not sure what it’s called trying to learn as I go
 

tsemmett

Active Member
Jul 2, 2019
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There's a code on the side of the PCM, behind the passenger side kick panel (bottom portion in front of the door). Examples here.

Some of the V6 models I'm seeing are: YYG3, TBX3, YYG3
While GTs include: NUX2, NUX1, MHS2

But yeah, grab the code off it and see if you can find what it matches.
 

Petericaza

Member
Dec 3, 2019
66
2
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48
San jose
There's a code on the side of the PCM, behind the passenger side kick panel (bottom portion in front of the door). Examples here.

Some of the V6 models I'm seeing are: YYG3, TBX3, YYG3
While GTs include: NUX2, NUX1, MHS2

But yeah, grab the code off it and see if you can find what it matches.
Alright I will do that after school today, just wondering if it’s a v6 computer would I buy a gt 2004 computer or a 1999 gt computer? Asking because the v6 was swapped with a 99 gt engine. And would that also fix my speedometer not moving from 0? Thanks for the help.
 

tsemmett

Active Member
Jul 2, 2019
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Everything I'm seeing on that PCM suggests it's for a 4.6 with a manual trans. Should be usable, if it's good. Get a test light/multimeter and check wiring like Wmburns suggested.
 

Petericaza

Member
Dec 3, 2019
66
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San jose
Everything I'm seeing on that PCM suggests it's for a 4.6 with a manual trans. Should be usable, if it's good. Get a test light/multimeter and check wiring like Wmburns suggested.
Oh thanks I will do that after school today but I also want to ask if you guys would know why when I turn my wheel or press the breaks at idle it makes a buzzing sound from the engine would that be because the brake booster wasn’t changed to a 4.6 and also the ari conditioner come out warm and like every few seconds a loud woodpecker like sound comes from a pulley on the engine I will send a pic after school
 

tsemmett

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I'm betting the brake booster was changed; the 3.8 one is supposed to be too wide for the 4.6 (I know my brother had to change his when doing this swap in his 98).

The 4.6 booster is hydraulic, using the power steering system, so it makes sense that you'd hear the pump whine when hitting the brakes and turning the wheel (vs just when turning the wheel on a 3.8 brake system). Check the power steering fluid; could just be a little low.

The other noise is your AC Compressor short cycling (turning on and off too fast). Most likely the charge is off, though a bad sensor can do this. If you're not familiar with HVAC systems, you might send it to a shop for this one. It's illegal to vent the refrigerant, and without the proper gauges, it's next to impossible to tell what's really going on. Many people will just charge it (with one of those cans that has a single gauge), but if you have a leak, you may risk further damage to the system (the refrigerant carries oil for the compressor).
 

Petericaza

Member
Dec 3, 2019
66
2
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48
San jose
I'm betting the brake booster was changed; the 3.8 one is supposed to be too wide for the 4.6 (I know my brother had to change his when doing this swap in his 98).

The 4.6 booster is hydraulic, using the power steering system, so it makes sense that you'd hear the pump whine when hitting the brakes and turning the wheel (vs just when turning the wheel on a 3.8 brake system). Check the power steering fluid; could just be a little low.

The other noise is your AC Compressor short cycling (turning on and off too fast). Most likely the charge is off, though a bad sensor can do this. If you're not familiar with HVAC systems, you might send it to a shop for this one. It's illegal to vent the refrigerant, and without the proper gauges, it's next to impossible to tell what's really going on. Many people will just charge it (with one of those cans that has a single gauge), but if you have a leak, you may risk further damage to the system (the refrigerant carries oil for the compressor).
The power steering would make sense because last night it was a little below the min line but I didn’t think that was the reason it was making a loud sound and for the ac compressor I’ll try and get someone to extract it and use chrisfix YouTube video to fix it. If I end up needing a new part could I use a 2004 gt for parts or does it have to be a 99gt part my engine is a 99gt
 

tsemmett

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It depends on the part; if it's external to the engine (AC/Power Steering/Alternator, etc), it should work. Anything else you should double check on; the 99 engine is from the Windsor plant, while the 04 is from the Romeo plant. There are differences in the longblocks.
 

Petericaza

Member
Dec 3, 2019
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San jose
It depends on the part; if it's external to the engine (AC/Power Steering/Alternator, etc), it should work. Anything else you should double check on; the 99 engine is from the Windsor plant, while the 04 is from the Romeo plant. There are differences in the longblocks.
Thanks for the help I’ll do my research. Ima be honest I don’t know how to check the injectors for I just put my test light on it and it lights up? Or what? Also my speedometer doesn’t work at all so I’m confused on why it’s like that if the cpu is a 4.6
 

tsemmett

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For testing the injectors, check this out, he goes over a couple methods and does a pretty good job of explaining how this works. Youtube

Does the speedo register 120 or 150? I wouldn't think a V6 speedo would be an issue, but I also don't think I have seen anyone do this swap on a 99+ car (98 and earlier doesn't have PCM controlled gauges).
 

Petericaza

Member
Dec 3, 2019
66
2
8
48
San jose
For testing the injectors, check this out, he goes over a couple methods and does a pretty good job of explaining how this works. Youtube

Does the speedo register 120 or 150? I wouldn't think a V6 speedo would be an issue, but I also don't think I have seen anyone do this swap on a 99+ car (98 and earlier doesn't have PCM controlled gauges).
It registers 150 and the the needle moves when I do a gauge check on the car by pressing the trip button. I plugged my obd 2 in and it’ll tell me the speed the speedometer still won’t move
 

tsemmett

Active Member
Jul 2, 2019
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If it were me, I'd focus on the injector issue first, as the diagnosis of it is more straightforward. A bad injector driver will require a new PCM either way, and it very well could be that yours is bad.
 

Petericaza

Member
Dec 3, 2019
66
2
8
48
San jose
If it were me, I'd focus on the injector issue first, as the diagnosis of it is more straightforward. A bad injector driver will require a new PCM either way, and it very well could be that yours is bad.
Thanks for sticking with me to help though I really appreciate it:)