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Hey guys, just working on a 91 rt tt, car sputters bad under load, surges at idle, etc. The problem is intermittently worse. I came across some sites saying these cars suffer from ecu issues so I checked into this one. Should I be sending this away to one of the repair places? If so, I could use some recommendations on who to use or who to stay away from, thanks
285391
 

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Uummm I'm going to go out on a limb and say yes it looks like it could be a problem. I am absolutely no expert on the matter but yeah that would seem to me to be something that would likely effect the circuit board traces but I don't know what that jumper goes to. Maybe somebody can help out who knows more about the boards than me. I would definitely find out what could be affected.
 

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Yeah I was just hoping somebody would know if the area of damage on mine is common to symptoms like mine. Sputtering and feels like a misfire under load. Thank you
 

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First thing I would do is put some rubbing alchohol on a q-tip and see if you can clean up some of that mess.
Then I would take a multi-meter (set for resistance/ohms) and see if there are any shorts between the devices that look "bridged" in those pictures.

If I had to guess I would say that at some point during original build of your circuit board, there needed to be some touch up done on some of the solder joints, and extra "flux" was used.

That "flux" is what caused your contamination issues (it should have been cleaned/removed, but the tech got lazy).

You "may" be able to fix the problem just with cleaning....

Bob.
 

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Above is who I used very friendly honor warranty, no questions. Tell them Dave a. Referred you, they have mine right now for second time in a year. Couldn't find a problem so them supplied a different ECU, just got notice today it is in the mail.
 

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Discussion Starter #7
Thanks guys, i ended up sending it SIA electronics a few days ago. They say they have done many of these ecu’s.
 

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I also had a major problem with a failed ECU on my '91 GT3000VR4. Ultimately, the injectors were "on" full time, dumping fuel into the cylinders. You have probably seen the reference to the electrolytic capacitors (4 I think) failing in the 1991 ECU's. Because the injectors were full on 100%, those power resistors (blue in your photo) that feed the final 6 power transistors driving the injectors failed and several burned out. I replaced the electrolytic caps with mil temp parts, replaced the power resistors and the ECU fired up like the day it left the showroom. I may have written more about it several years ago, you might look up my old posts, there may have been photos.
 

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Discussion Starter #10
Thanks I will look for those older posts and read up, good to know those 6 blue resistors are part of the injector circuit.
 

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Thanks I will look for those older posts and read up, good to know those 6 blue resistors are part of the injector circuit.
You might want to ohm test windings in your IAC, I seem to recall if a winding shorts to ground it can damage injector circuit in ECU. I don’t know if taking out those resistors is what happens though, but if so might damage rebuilt ECU if IAC does have a short.
ISC or IAC.jpg

ISC servo. Press down on the release lever of the wiring harness connector and pull it off the ISC servo. You may have to wiggle it a little as you pull. Do not pull on the wires. At this point you can test the resistance of the four coils or wait until you have the ISC servo off the throttle body. To perform this test, measure the resistance between terminals 2 and 1, between 2 and 3, between 5 and 4, and between 5 and 6. The resistance should be in the range of 28 to 33 ohms for the original and older models, and ~40 ohms for the most recent model (black ones), which is after our 3S cars were manufactured.
 

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Discussion Starter #13
SIA electronics did a good job, great pricing, and provided quick service. Car runs excellent now. Thanks
 
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