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Discussion Starter · #21 ·
I got under the hood last night and sprayed brake clean around #8, no change in idle. I also wiggled wires around to look for a loose connection, no changes either. I'm going to dig around in my parts bins and try to find a spare ECU to swap out. She has seemed to develop a slight rough idle when cold. So that will aid in troubleshooting.
 

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Discussion Starter · #22 ·
Got the ECU swapped out. I forgot how much of a PIA that is. She runs real well, no codes so far. Fuels trims were hovering around 0 when I looked at live data, but unfortunately data logging did not work on my way into work today. I need to make sure the logging works on the way home so I have some data to look at.
 

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Discussion Starter · #23 · (Edited)
It happened again on the way home today, 95+ degrees out and dry. I've recently replaced all 8 fuel injectors. Yesterday I got her all back together from replacing the radiator, water pump & hoses. I also replaced the #8 spark plug wire only. I disconnected the battery while doing that work, so the ECU was cleared when I put everything back together.
This eliminates pretty much everything. I need some input into where to look next. Thanks.
 

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Look closely at the coil packs; I had one crack near the mounting holes, and it was leaking spark.
I put it in my dry box, and baked it dry. I then pulled a vacuum on it, and coated it with humaseal. No more problems.
 

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Discussion Starter · #25 ·
Good point and I will check that, but I did swap coil packs when this first happened.
I'm also going to look at the wiring input to the coil packs.
I've read about mechanical issues causing this code. If this was mechanical defects wouldn't this be more constant?
ie a valve not sealing correctly wouldn't be this intermittent.
 

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1995 Thunderbird LX 4.6 red
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Can you aquire another computer cheap? If so swap a different ECM in and see if repeats.
 

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Discussion Starter · #27 ·
Just so happen to have a 3rd ECU I recently grabbed from the junk yard.
I Ohmed out the red/yellow wire from the coil pack to the ECU, this should be the trigger wire for plug #8. 0.2 Ohms with no variation wiggling the wires.
With the 3rd ECU I found some bent pins, straightened those up and installed it. Seemed to run fine, it did have a pending P0340 code, first time I've used this ECU so I have no clue of it's history.
When looking under the hood there is some ticking coming from the back of the engine, so I shut it down and went back to the other ECU.
Ticking is still there with the other ECU, there's also what sounds like crackling, like electrical arcing, but I could not see any arcs.
This is getting beyond my familiarity, so I'm sharing a link to a video. The ticking sounds more like knocking in the video and the kind of random pops are the crackling I'm referencing above.

 

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1995 Thunderbird LX 4.6 red
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Yeah, in the video that sounds like arcing. You could try and unplug a spark plug wire one at a time to see if the ticking stops when one particular cylinder is deactivated. Just so I'm clear you get the ticking with any of your ECMs?
 

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Discussion Starter · #29 ·
ECM1 = original
ECM2 = the one I've been running for about a month
ECM3 = just nabbed from the bone yard

Today with ECM3 I heard the ticking, but not the arcing (could have missed it).
Switched back to ECM2 ticking still there and heard the arcing this time. Had to step away, think this through and haven't been back. I'll try pulling the wires and see what happens.
 

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If you hear spark arcing, then you have a bad plug, wire, or coil. There is no way for a bad ECM to cause spark to leak out of one of those.
 
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Discussion Starter · #31 ·
If I pull wire 2 or 8 the arcing goes away. I already replaced #8 wire so I replaced #2 wire, no change, at least not significant. Pulled #2 plug, it's bad. See pics below. It's white and some of the electrode is melted away.
These are NKG iridium and less than 5 years old, so I think these should have lasted longer. It runs much better, but there still is a rough idle so I'm going to order new plugs & replace all the wires while I'm at it.

 

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1995 Thunderbird LX 4.6 red
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Interesting. 2 and 8 are on the same side of the drivers side coil. Forgive me if you already said this, but have you replaced the coils? Try swapping the coils if you haven't.
 
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Discussion Starter · #33 ·
Yes, so 2 should be the waste when 8 fires, that would explain why plug 2 is bad and it's affecting and throwing the code for #8. I do not have any spare coil packs, but I did swap the left & right coil packs when this first happened. The code has always pointed to #8. If both coil packs were bad I should see issues with 3 & 5 also.
 

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1995 Thunderbird LX 4.6 red
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Yes, so 2 should be the waste when 8 fires, that would explain why plug 2 is bad and it's affecting and throwing the code for #8. I do not have any spare coil packs, but I did swap the left & right coil packs when this first happened. The code has always pointed to #8. If both coil packs were bad I should see issues with 3 & 5 also.
Yeah, that would make sense. Let us know how it is after the new plugs and wires.
 

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Discussion Starter · #35 ·
To give some more background: about 2 weeks ago I replaced the fuel injectors. While testing the old ones; 1 leaked, but then sealed up after exercising it a few times, a 2nd one leaked and I ran out of carb cleaner while testing.
So I had potentially 2 leaking injectors.
A few months ago one of my heater hoses blew, I was able to cut the split out and bend it back, babied the car to the gas station and filled it up with bottled water to make it home.
Then last week the radiator went out (upper radiator hose connection broke) dumping all my coolant again, I band aided it again, but she did not make it home, had to get a tow. Neither of those times did I let the car overheat.
I have some new spark plugs on order, they should be in this week and I'll throw those in with the rest of the new wires and report back.
 

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I would not run iridiums. Stick with the original type, platinum. Or even just plain copper will work.

Al
 

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Discussion Starter · #37 ·
#8 wire pulled off the plug real easy, so I'm wondering if it was loose. Non of the other plugs looked fouled or bad in any way.
Got the plugs and wires replaced. Took her for a drive and things seem to be in good shape. The real test will be tomorrow going to work. I'll update tomorrow.
 

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Discussion Starter · #38 ·
She ran really well back & forth to work today. There's a little bit of a rough idle at times, I'm going to have a buddy of mine take a look at give me a 2nd opinion.
 

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1995 Thunderbird LX 4.6 red
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Good to hear. Go run the gunk out of her!
 
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