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I bought a 91 Stealth TT a few months ago from a junkyard (for sale area not picking area), got it cheap since the engine torn apart for 60k service it's at 78k miles, everything except maintenance parts were in the trunk. After buying the 60k service kit, thermostat, balancer and power steering pump with tensioner, to switch to serpentine ps belt since the balancer was among the missing items, engine went back together with only major hiccups were a coolant leak and dead fuel pump, fixed those also got a fuel filter. I've never owned one of these cars but it seemed like everything was there, started up fine and left it to warm up to see if it would overheat, no issues but before the day ended it started to break up and wouldn't accelerate. My dad thought maybe it just needed to be driven since it'd been sitting for so long, it was pretty obvious that the car has been sitting for at least a year with corrosion and build up in and around the cooling system, next thing we know there's smoke coming from the foot well, burned ecu.

TLDR: bought car in unknown condition, did 60k service > cars ok> cars not ok > burned ecu.

Other things I noticed while trying to get it working were the "Engine" fuse the footwell was burned out, have no idea when that happened didn't notice until trying to start it replaced and it didn't go out again, noticed a static buzzing kind of sound coming from the idle air control valve although unplugging it and plugging it back seemed to get rid of it temporarily.

On to the ecu I just want to know if there's any known issue in this way, I know about the capacitors due to age and drivers due iacv (I think that's right) but those didn't burn out. The burn seems to start near pins 103 and 104, third and fourth pins from the top left of the middle plug on the top side and the back near what appears to be a grounding pad I suppose. Like I said I just want to know if there's some other know issue or if someone else is able to more easily pinpoint what happened from this, or if it's just a shot in the dark and need to start looking for a short.

It burned in front of one of the capacitors although the capacitor seemed ok.
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Closer picture of the burned area, most of the stuff to the right seems to just be black from the smoke created from the burn.

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Pics of the back of the ecu.

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Picture pointing to the capacitor lead on the back of ecu with a screwdriver.

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Not sure if this was a direct result of the ecu it self since the the plug seems to have been unaffected.

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Here's a link to a google drive folder with the pictures and couple extra ones.



Modifications:
There was already a greddy turbo timer although I turned it off while working on it, there was also some kind of cd changer (I think).
The only thing I did was a 3SX hot wire kit when I installed the fuel pump went with a walbro 255
 

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Discussion Starter #2
Update: I removed the capacitors, the ones near the burn is a little toasted but still shows 48.5μF out of the 47μF it should be, the middle one which seems to have been leaking shows 60μF out of 100μF and the smallest one show 23.7μF 22μF.

Pics of the capacitors and board with them removed.

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The capacitor nearest to the burn.
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Sounds like you pretty much know about all the issues with our ECU's (mostly 1g, but there have been 2g ECU's that suffer the same fate, failing capacitors).
Your's is definitely toast.
As for your IAC, while it probably did not cause the issue in this case, I certainly would pull it and test its resistance (procedure is spelled out in the manual).

I would NOT, repeat would NOT, get a replacement ECU and just slap it in the car. If the IAC is bad (and you don't follow the above advice), you could wind up with another damaged ECU.

Pretty sure the ENGINE fuse blew when the short in the ECU caused it to go up in smoke.

Shitty way to start a relationship with this car, but don't get dissapointed, I think you can get this running right....

Bob.
 

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Discussion Starter #4
Sounds like you pretty much know about all the issues with our ECU's (mostly 1g, but there have been 2g ECU's that suffer the same fate, failing capacitors).
Your's is definitely toast.
As for your IAC, while it probably did not cause the issue in this case, I certainly would pull it and test its resistance (procedure is spelled out in the manual).

I would NOT, repeat would NOT, get a replacement ECU and just slap it in the car. If the IAC is bad (and you don't follow the above advice), you could wind up with another damaged ECU.

Pretty sure the ENGINE fuse blew when the short in the ECU caused it to go up in smoke.

Shitty way to start a relationship with this car, but don't get dissapointed, I think you can get this running right....

Bob.
Thanks for the input I actually planned on replacing the IAC with the ecu anyway, figured if it's making noise even if it's still good it's probably on it's way out. As for the ENGINE fuse it was actually burned before we started the car, didn't think to check it after the smoke show just wanted to know what was burning. Won't be able to look into it some more probably until the weekend since the car is at my parents house instead.
 

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Ok I just found out the fluid that leaks out is actually conductive and will cause a short, thought it would just cause it to not work correctly and upon further inspection there is definitely some residue near the cap closest to the burn. Guess I just had an unfortunate accident with a leaking capacitor.
 
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