Swapped to v8 still thinks it's a 6 - TCCoA Forums

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post #1 of 19 (permalink) Old 01-10-2017, 09:15 PM Thread Starter
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Swapped to v8 still thinks it's a 6

I recently swapped a 97 4.6 into a 96 3.8 Thunderbird. I switched the computer and the v8 wiring harness and after firing it back up it only runs on 6 cylinders. I don't have cylinders 2 or 8. I swapped coils left to right and the same cylinders are dead leading me to believe the coils are good. I don't know how to diagnose this, it seems if the coil is getting power all four posts should work. I have 2 codes p0340 and p0350 I don't get oil pressure either but I believe i need to swap to the 96 pressure sender and the wiring is the same? Also need to make sure the temp gauge is working seems to stay way to cool, the fan is working because I hear is cycling on and off. I drove the 4.6 car home so I know it ran good, I swapped rear ends but left the fuel tank as the pumps have the same part number v6 to v8 which seed a bit odd. This is killing me because my wife is driving an V8 Excursion 60 miles round trip to work until I get her car back on the road. So A N Y help will be appreciated! I need to convince this car its no longer a v6, It needs to let go its a big boy now and needs to step up.
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post #2 of 19 (permalink) Old 01-10-2017, 09:27 PM
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I recently swapped a 97 4.6 into a 96 3.8 Thunderbird. I switched the computer and the v8 wiring harness and after firing it back up it only runs on 6 cylinders. I don't have cylinders 2 or 8. I swapped coils left to right and the same cylinders are dead leading me to believe the coils are good. I don't know how to diagnose this, it seems if the coil is getting power all four posts should work. I have 2 codes p0340 and p0350 I don't get oil pressure either but I believe i need to swap to the 96 pressure sender and the wiring is the same? Also need to make sure the temp gauge is working seems to stay way to cool, the fan is working because I hear is cycling on and off. I drove the 4.6 car home so I know it ran good, I swapped rear ends but left the fuel tank as the pumps have the same part number v6 to v8 which seed a bit odd. This is killing me because my wife is driving an V8 Excursion 60 miles round trip to work until I get her car back on the road. So A N Y help will be appreciated! I need to convince this car its no longer a v6, It needs to let go its a big boy now and needs to step up.
Did you swap the wiring harness between the ECU in the passenger side kick panel that leads to the engine harness connection on the passenger side of the cowl panel?

97 Thunderbird LX (The GT Bird)
PI Swapped NPI motor with some port work on the heads, PI cams, 80mm MAF, CAI that feeds from fenderwell. Jmod, 3.73:1 TL in Mark VIII carrier, Mark VIII aluminum LCAs, 93 Mark VIII driveshaft, PBR brakes (soon to be Cobras), 18x9 wheels, 255/40/ZR18 Tires, Front and Rear strut/shock bracing, GR-2 shocks, Eibach 1.5" springs, 1989 SC front and rear sway bars.
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post #3 of 19 (permalink) Old 01-10-2017, 09:49 PM Thread Starter
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I did not, just the engine harness. from all I read it was computer and engine harness. If that could be the culprit I'll do it tomorrow for sure. Do you happen to know if it is part of the main dash harness?
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post #4 of 19 (permalink) Old 01-10-2017, 10:02 PM
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I did not, just the engine harness. from all I read it was computer and engine harness. If that could be the culprit I'll do it tomorrow for sure. Do you happen to know if it is part of the main dash harness?
I don't know for sure, but I think it's a direct connection between the engine connection and the ECU in the fenderwell.

A friend of mine is doing the same swap, and noticed that there are a couple of connections in the V8 connection that aren't in the V6 harness.

97 Thunderbird LX (The GT Bird)
PI Swapped NPI motor with some port work on the heads, PI cams, 80mm MAF, CAI that feeds from fenderwell. Jmod, 3.73:1 TL in Mark VIII carrier, Mark VIII aluminum LCAs, 93 Mark VIII driveshaft, PBR brakes (soon to be Cobras), 18x9 wheels, 255/40/ZR18 Tires, Front and Rear strut/shock bracing, GR-2 shocks, Eibach 1.5" springs, 1989 SC front and rear sway bars.
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post #5 of 19 (permalink) Old 01-10-2017, 10:20 PM Thread Starter
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ok thanks for the insight, I'll look and see if its a separate harness. I just switched the CCRM with no luck. This is making me crazy!
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post #6 of 19 (permalink) Old 01-10-2017, 10:23 PM
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That harness isn't a direct interchange between the 96-97 I'll check my EVTMs if there's a pinout difference at the engine or EEC, there shouldn't but it's possible

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post #7 of 19 (permalink) Old 01-10-2017, 10:38 PM Thread Starter
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That would be incredible thanks! I just looked at the car and I believe he is right, I think that harness is my issue. The 96 is the the car that now has the v8. So it was a 97 4.6 that went into 96 3.8 if that makes a difference on pinouts. Thanks for all the help guys!!!!
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post #8 of 19 (permalink) Old 01-11-2017, 12:25 AM
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Looks like what are missing from that harness are the #7 and #8 fuel injector wires, and the coil wire for cylinders 2 and 8, so you were actually a V5 Weird, I had always thought these wires were included in all harnesses and just left them unused in 6 cylinders to simplify manufacturing, the rest of the harness is otherwise totally identical between V6 and V8. Never underestimate penny pinching Ford leaving a few feet of three unused wires in a V6.


So... if you're good at soldering you can use that harness from the 97 in your 96, but what you'll have to do is cut and splice the two connectors that join it to the dash wiring, which is about 34 wires to splice total. Not fun, and probably not reliable(asking for shorts having that many splices next to each other, no matter how good you are) Best and easiest option then would to be to either find a complete 96 V8 EEC harness from a junkyard. OR the not so easy option, which will require some harness building skillz but no splicing: unwrap the 97 harness and convert your 96 harness to V8 spec, removing the complete wires terminal to terminal(no cutting) from the 97 harness and adding them to the 96 harness. That would be:

Fuel injector #7s tan/red wire from pin 72 on the EEC connector(you may have to drill the hole in the connector face if it's filled) to pin 20 on the engine harness connector (which may have a filler wire you discard)

Fuel Injector #8s light blue wire from pin 98 on the EEC connector to pin 21 on the engine harness connector

Coil driver #4s red/yellow wire from pin 104 on the EEC connector to pin 41 on the engine harness connector


Excessive option but I felt it worth providing. The EEC connector and engine harness in-line connector are numbered though so it wouldn't be as hard as you'd think. Hardest part would be unwrapping and rewrapping the tape.
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post #9 of 19 (permalink) Old 01-11-2017, 09:40 PM Thread Starter
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absolutely amazing, thank you both for the super fast help. I'll have this thing running in no time. I will build the harness to spec thanks to the pin location. I've built wire harnesses before so its not a big deal when pointed in the right direction. I'll post back this weekend when i build it. Thanks again guys
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post #10 of 19 (permalink) Old 01-14-2017, 03:51 PM Thread Starter
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Well I added the 3 wires from the 97 harness and it fires right up and runs smooth. I still get the P0340 cam circuit malfunction, so it stumbles on acceleration and when I put it in gear. I also installed a 96 mechanical oil sending unit sender and still get no oil pressure when its running. If I ground the sensor wire the gauge inside climbs up. Also the coolant gauge is not working. I came across something in my readings that stated someone had to ground the instrument cluster? Does this sound correct and could this be my problem? The tach seems to be pretty high for a 4.6 I need to figure out what pins to test and see if the circuit is damaged somewhere. Does anyone know if these harnesses can be bought new somewhere? I'd hate to put a junkyard harness in with old brittle wires to have more issues later. I can deal with the gauges not working if I can get the cam issue handled. I swapped the cps out with a new Ford one to so thats not the issue and I stripped back a little of the wiring and that all looks pretty good. I'd rather test it before cutting the harness open. Thanks in advance guys
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post #11 of 19 (permalink) Old 01-14-2017, 04:47 PM
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If your intake manifold has the factory plastic coolant crossover you may be lacking ground for the sensor itself, the aluminum crossovers don't need a ground for the sensor since the sensor body grounds through it. If so the ground wire off the sensor is black/white, so if you ground that to something metal on the engine the gauge should work correctly, there may actually be a spade connector on the harness to ground to a bolt for this very purpose but it's been a long time since I looked at a 97 harness and could be mixing things up.

The Tach is the one you ground from the cluster, that would be pin 1 of the larger connector. It may still read a bit off but there's a little potentiometer on the tach's internal circuit board that is used to calibrate it. Easily done if you have a scan tool to monitor revs, otherwise find a V8 tach or doner cluster and swap it in.

I'm a little unclear about oil pressure, when you say you swapped in a 96 mechanical sending unit, does that mean a stock factory sending unit that is a 6psi switch? Or a sending unit that actually reads accurate oil pressure? If it's the latter you need to bypass the resistor for the gauge to properly read. If it's the former I'm not sure what's wrong since the circuit is the same between the 3.8 and 4.6, it grounds through the sensor body on both with 1 wire from sender to cluster. I'd check the connection as those slip on connectors can gum up and corrode as well as the engine harness for damage - it's easy to break that wire when removing the harness since there's so much around it.

Cam position may actually be a PCM fault, that's been an often reported symptom of a bad one with no problems related to the sensors or wiring. Still worth double checking but they may not be the problem
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post #12 of 19 (permalink) Old 01-14-2017, 07:08 PM Thread Starter
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Yes its a factory switch for a 96 that came equipped with a actual gauge not the dummy light, I believe the 97 just had the light which is why I bought the new switch hoping that would fix the issue. The wiring is clean While the engine was out I put new gaskets in it cleaned everything out re tapped holes, and put di eclectic grease in everything. The harness looked really good I know with age especially in Az things get brittle, I was careful with it though. Where is the best place to obtain a EVTM for these cars? I need to find the wires to test for wiring issue before just buying a computer. The intake is new and it has the aluminum crossover
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post #13 of 19 (permalink) Old 01-14-2017, 08:51 PM
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Yes its a factory switch for a 96 that came equipped with a actual gauge not the dummy light, I believe the 97 just had the light which is why I bought the new switch hoping that would fix the issue. The wiring is clean While the engine was out I put new gaskets in it cleaned everything out re tapped holes, and put di eclectic grease in everything. The harness looked really good I know with age especially in Az things get brittle, I was careful with it though. Where is the best place to obtain a EVTM for these cars? I need to find the wires to test for wiring issue before just buying a computer. The intake is new and it has the aluminum crossover
As was mentioned above, the "real" oil pressure gauge in our cars is just an analog idiot light. It reads "normal" at anything over 6psi. To make it a "real" gauge, you need to wire in a resistor around the gauge, instructions are here on the board... How to convert your oil pressure gauge (with pics)

That said, if you have the original pressure sender, install it and see if the gauge suddenly works. If it does, you just need the resistor to go with your new oil pressure sender.

As for the EVTM... https://www.dropbox.com/s/vps05bv69o...acuum.pdf?dl=0
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97 Thunderbird LX (The GT Bird)
PI Swapped NPI motor with some port work on the heads, PI cams, 80mm MAF, CAI that feeds from fenderwell. Jmod, 3.73:1 TL in Mark VIII carrier, Mark VIII aluminum LCAs, 93 Mark VIII driveshaft, PBR brakes (soon to be Cobras), 18x9 wheels, 255/40/ZR18 Tires, Front and Rear strut/shock bracing, GR-2 shocks, Eibach 1.5" springs, 1989 SC front and rear sway bars.

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post #14 of 19 (permalink) Old 01-15-2017, 02:12 PM
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For some reason I'm thinking the 97 is backwards, and uses the Mark sender...

Anyone know for sure?

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post #15 of 19 (permalink) Old 01-15-2017, 02:56 PM
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Yes, the 97 one is normally closed, opening with oil pressure, turning off the light. The 96 one is normally open and closes with oil pressure moving the needle to "norm"
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post #16 of 19 (permalink) Old 01-19-2017, 09:36 PM Thread Starter
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Is it normal for these cars to run with the cam sensor completely unplugged? I am beginning to believe I am going to need to tear the front of the motor apart again. Is there a way you can check timing on these cars without tearing the cover off to see if it is off a tooth maybe? It runs great I cant imagine it being off the way it runs.
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post #17 of 19 (permalink) Old 01-20-2017, 02:18 AM
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Quote:
Originally Posted by Grog6 View Post
For some reason I'm thinking the 97 is backwards, and uses the Mark sender...

Anyone know for sure?
Quote:
Originally Posted by XR7-4.6 View Post
Yes, the 97 one is normally closed, opening with oil pressure, turning off the light. The 96 one is normally open and closes with oil pressure moving the needle to "norm"
Oil Pressure Switch/Sensor Information

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post #18 of 19 (permalink) Old 01-24-2017, 07:27 AM
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If the sensor and wiring are good, cam timing could be an issue. I've seen that before on a 2.3 focus. The cam and crank sprockets slip over time because there is no key way. I also had this code a couple months ago. Swapped a 09 4.6 2v into a 03 f150. Turns out some time in 08-09 the lh sprocket got 8 exciter teeth instead of 1. Unhooking the sensor made the bad running go away until I got a new sprocket.
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post #19 of 19 (permalink) Old 01-24-2017, 03:51 PM
No, Mr. Lemmywinks, No!!!

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God, I'm getting old.

Now I remember testing all that here on the bench, as I had both sensors sitting there.
And one from a Town Car, which is also the "open on pressure", later type.


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