Resolved 1990 dsm ecu repair strange issue

[sakroda]

hello
my talon has low power(hp) when it s warmed and i wonder about ecu condition and i removed i saw burned something it does not look like leaking or something else what do u recommend for fix i have 2 ecu’s i can replace capacitors or something else

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[steve]

For some reason the 90 ECUs like to have that front capacitor dry out and short, often burning through the circuit board under it.

 

[sakroda]

For some reason the 90 ECUs like to have that front capacitor dry out and short, often burning through the circuit board under it.

ohhhh steve thanks for reply i mean this smoke is came out from capacitors 2 numbered or number 1 circuit? do u have an idea?

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[steve]

The C106 you've labeled #2 shorted and burnt coating #1 when it did.
You are likely going to find the PCB under the capacitor burnt and one of the ISC traces melted that runs under the capacitor.

All 1G ECU's need the caps replaced but the 90's more so because they tend to do this.

 

[sakroda]

The C106 you've labeled #2 shorted and burnt coating #1 when it did.
You are likely going to find the PCB under the capacitor burnt and one of the ISC traces melted that runs under the capacitor.

All 1G ECU's need the caps replaced but the 90's more so because they tend to do this.

thanks steve actually i have hot start problem i thought problem is the ecu and i tried with another ecu it s same it does not work very well on hot start... rev is 350 and it dies sometimes or it try to keep on 500 rpm so one minute later it s going to 750 rpm and car stalks..
so do i have to change labeled #1 i guess i have to change label # 1 also?
i attached another ecu pic maybe i can replace parts from another ecu?

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[1990TSIAWDTALON]

Machv and RTM both carry a capacitor repair set. Just FYI.
Just click on their names for the kits.
Thanks for your help @steve. It is greatly appreciated!
Marty

 

[steve]

I'm sure it's much easier to source a handful of capacitors in Turkey that it is to get MachV to ship there. Like it says in the RTM ad, the caps are 22uF@50V, 47uF@50V, 100uF@25V.

C106 is the 47uf, C107 is the 22uf, and C108 is the 100uf.

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I don't expect the white hybrid IC you marked as 1 to be damaged just covered in the smoke from the burned C106 cap. If you look above the circuit trace between the + and - leads of C106 is for one of the ISC coils. if it's damaged the ISC won't step correctly and it one of the ways you can have idle control issues.

The other ECU doesn't look much better than the first overall.

 

[sakroda]

thank you i will replace them and i will share the results

 

[sakroda]

thanks for everything i replaced the capacitors and hot start issue is gone
@steve

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[steve]

Yep, that's pretty much what I expected.

 

[sakroda]

Yep, that's pretty much what I expected

Today I tired to fix base idle BISS I am telling what i did:
1) I connect the ignition timing connector to ground
2) I connect the third pin to ground on diagnostic port
and adjusted rpm from biss but even tight the biss until to end
so rpm is still on 1100 rpm
i have checked the ohms of my ISC it shows 0,30 ohms each pin
i replaced another ISC it s same.what do you think about it?

 

[1990TSIAWDTALON]

Loosen up the accelerator cable and make sure it isn't holding the throttle open. If that is all good, adjust the idle stop switch to lower the idle speed.

 

[sakroda]

Loosen up the accelerator cable and make sure it isn't holding the throttle open. If that is all good, adjust the idle stop switch to lower the idle speed.

I did it but my problem is different i guess
I adjusted to rpm on 750 everything is fine but i stop the engine and remove the ground cables after then start the engine it still keeping on 750 but when i drive the car for 100 m it s going up to 1100 rpm it was 1300 rpm i changed the ISC it s on 1100 rpm right now

 

[yokotabrat]

I might have missed it, but if you only replaced the capacitors in that ecu that you have a picture of in post # 9 and didn't repair the trace that is under it, your ISC will not work properly. That trace goes to one of the ISC drivers, so you'll have to get that repaired before it works. There's also a good chance the ISC driver is bad also.

 

[sakroda]

I will change the capacitors of my another 1990 ecu and we will see it..

 

[1990TSIAWDTALON]

I agree with @sakroda, and never thought to remind you that the trace got toasted so you'll need to make a jumper out of some telephone wire or such (its what i use).

 

[sakroda]

@steve I need your help about 1991 ecu on my 1990 I read a lot of article but I am confused if i swap the ecu's between them, Do i only swap pin 6 and 14 or Do i need swap also PTU or coil system? if i swap 91 ecu my cluster will not work out? rpms?

 

[steve]

Yes, at minimum you have to swap pins 6 and 14 but the gauge cluster tachometer (rpm) won't work correctly. Pins 6 and 14 changed their functions between the 90 and 91+ ECU's.

There were several ways to fix the tachometer, the simplest was the old Keydiver circuit board that went into the ECU but they are long gone.

The rest start replacing parts of the 90 ignition with the later parts.

You can modify the Power Transistor wiring to use the 91+ PTU and run the ECU tach pulse from it leaving the 90 coils, tach gate, and noise filter connected to the gauge cluster to drive the tachometer.

The full treatment was to swap the 91+ PTU, coils, and gauge cluster in.

Fixing the 90 ECU seems like an easy option compared to modifying the engine harness and running a new tach signal to the ECU.

 

[sakroda]

Yes, at minimum you have to swap pins 6 and 14 but the gauge cluster tachometer (rpm) won't work correctly. Pins 6 and 14 changed their functions between the 90 and 91+ ECU's.

There were several ways to fix the tachometer, the simplest was the old Keydiver circuit board that went into the ECU but they are long gone.

The rest start replacing parts of the 90 ignition with the later parts.

You can modify the Power Transistor wiring to use the 91+ PTU and run the ECU tach pulse from it leaving the 90 coils, tach gate, and noise filter connected to the gauge cluster to drive the tachometer.

The full treatment was to swap the 91+ PTU, coils, and gauge cluster in.

Fixing the 90 ECU seems like an easy option compared to modifying the engine harness and running a new tach signal to the ECU.

thank you it s clear now i guess i need to swap evo 8 ecu god bless you

 

[steve]

thank you it s clear now i guess i need to swap evo 8 ecu god bless you

Unless you can buy an adapter harness that makes the other rework look like childs play.
There are advantages to being able to use EVOScan and ECUflash but also lots to learn.