General Bad ISC Destroying ECU?

[bryce]

Hey guys, i recently did my clutch and after i went to fire her up and was running on 2 cylinders so i narrowed it down and it ends up my ecu was fried. so i tried another ecu and it did the exact same thing. Could it be my isc doing this?

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[yokotabrat]

Yes, the chip that is blown is one of two chips that drive the 4 isc coils. When the coils go low resistance, there isn't anything to limit the current and the chip gets fried.

I'm not sure that this would cause the car to run on two cylinders, though. The chip that's blown only controls the isc. When it goes, your idle will not be controlled correctly and therefore might run rough, but the car shouldn't drop cylinders.

 

[steve]

+1
This is a classic case of a bad ISC blowing the driver.

 

[bryce]

so maybe it was just running really choppy, it gave me a ignition coil code but the coil was fine. should i just try to block off the isc and give it a whirl? is there anyway i can do it without blowing a nother ecu

 

[tsunari]

No need to block it off for testing . . . just unplug it and give it a whirl . . . You wont have the best (read: any) automatic idle control, but you wont be blowing ECUs anymore.

time to get a new ISC :-(

http://www.stealth316.com/2-isc-iac.htm

On the up-side . . . your ECU's may be saved . . . might be as simple as installing new drivers.

 

[bryce]

it also looks like on the back side of the board. one of the caps seems to have a burnt spot on it too, its the cap that is closest to where the wiring harness plugs into. the top side of is not noticably messed up but on the bottom there are black spot and it looks burnt like the bottom of the other one.

Could the isc do this as well or could that just be a problem that occoured over time

k on the other ecu that i blew up the back of the cap is completely fine so i guess it was just that driver that blew up.

could the driver exploding cause something to only give me spark on 2 cylinders cause only 2 plugs are getting spark. my 2 and 3 cylinder are not gettin spark and i tried another completely working power transistor and coil and it did the exact same thing so those two things are ruled out.

could it be my isc blowing up that driver thats making it only run choppy on two or three cylinders or whatever it is?

please let me know asap guys this is killing me an i need to get the car to the track!

 

[bling5tatus]

Here's my question... is it possible to put resistors on the drivers so that in the case when the isc does go bad it will keep from blowing up the driver on the board?

Just a thought.

 

[yokotabrat]

When the isc drivers fail, they tend to cause the traces that route the current to the driver chip to fail also. The traces on the board aren't designed to handle a lot of current like when the isc shorts out. That could be the burnt spot you are seeing on the board.

The isc circuit is fairly separate from everything else as far as I remember. I don't believe it'll cause your no spark on 2 & 3 problem. Have you tried a known good CAS? That could also cause your problem.

Bling5status: I haven't designed any stepper motors so I'm not 100% sure, but I don't think adding a resistor would work. I think it would depend on how high a resistor you stuck in. Any added resistance is going to reduce the current which will reduce the magnetic field used to move the isc. If you reduce this too much the isc may no longer work without redesigning the number of turns in the isc coil to increase the magnetic field again. Again, not 100% sure, though.

 

[bryce]

could the cas be frying my ecu as well?

 

[tsunari]

Here's my question... is it possible to put resistors on the drivers so that in the case when the isc does go bad it will keep from blowing up the driver on the board?

Just a thought.

You wouldn't want to add a resistor . . . for protection against this you would either want to:

1) Buy a new ISC before it goes bad (maybe every 75k-100k miles)
2) wire in an inline fuse so it will blow instead of the driver/traces blowing

 

[bryce]

k guys so im still at an awe here.

i dont wanna go blowing up another ecu till i get some good info on what the hell is going on here. i know the isc is blowing up that driver but that the hell would only make it run on 2-3 cylinders.

when i pulled the ecu and checked and seen the damage i immediatly suspected just a bad ecu being an amateur with electronics so i swapped out for a different one and the same thing happend and then the guy that brought me the other ecu out of his car went home put it in and it did the exact same thing. it ran choppy and wouldnt fire on all 4, then i got him a good ecu and his car once again runs mint.

So there has to be some sort of problem within my electronics that is doing something that can cause it to not give those cylinders or cylinder spark.

Can a very very bad isc do this? I pulled the isc out and noticed that it didnt turn at all which i thought it was supposed to and noticed oil on it. is it possible that that is causing my problem or is it a possibility that my cas is bad and just pops the ecu too causing it to run so shitty.

With my logger on i get code 44 all the time, and i think the first time i did the scan there was code 12 and 14. I know code 44 is ignition coil and i know its not that or the transistor cause i got 2 working ones out of a buddies car tried them out and did the same thing, and then he went back and put them back in his car and they worked completely fine.

So there is just something messing with me now that i NEED to figure out , so anything you guys can do to assist me please let me know.

 

[oldman]

You have been here long enough to know bumping your thread is a no no and that using proper punctuation and capitalization is a must when posting in the tech forums, please comply to avoid closure of your thread. The answer to your question is clear, you need a new ISC.

 

[Loewen21]

So yes we've determined that the ISC is causing a problem but he's wondering where the ignition problem on cylinder 2 & 3 is coming from. We've checked for spark and there is none at all on those two cylinders but there is on 1 & 4. Could the CAS be frying the ecu?? Or what is causing this misfire problem as we know it isnt the wires, the spark plugs, the coil or the transistor.

 

[sniver]

I am having a similar problem I believe. The IC (driver) that is bad in mine is IC105 (second farthest IC from the outside edge in that cluster shown above).

What does that control/would cause it to burn up and could I switch the driver, along with the capacitors from a 90 n/t 5spd ecu (bought from advance auto parts less than a yr ago), into my 92 turbo auto ecu?

 

[bling5tatus]

I can tell you one thing and that's that it wouldn't be a good idea to switch capacitors out of any stock ecu into another ecu... just get new ones.

 

[steve]

+1 You don't reuse the capacitors, desoldering can damage them and the factory caps are junk to start with.

 

[tsunari]

so what's wrong with putting in a new ISC (or disconnecting the bad one) and drop in a good ECU?

 

[92awddsm]

It looks as if the 2 injector drivers above the isc drivers were heated enough to damage them. That may be causing the miss but Im not sure that it would cause a no spark situation. This is where Steve needs to jump back in.

 

[sniver]

Okay, that makes sense , so that also applies to the ic105; correct? So that ecu is garbage. However, does anyone know what ic105 controls so i don't fry another one like said above?

Current issues: Maybe Ic105 operates any of the following?

* One capacitor has leaked a little
* Fuel pump never turns off when the car key in at the ON position.
* At high load,mid to upper rpms, and boost over 9(stock gauge) car bucks like fuel cut. After some beating and getting it a little warm, it starts to work right. Then later after I'm nice it proceeds to screw up again.
* Isc erratic (have not tested it,just unplugged)

 

[bryce]

It looks as if the 2 injector drivers above the isc drivers were heated enough to damage them. That may be causing the miss but Im not sure that it would cause a no spark situation. This is where Steve needs to jump back in.

So if i unplug my Isc, will my ecu be ok? That would make sense that the injectors were not firing because i pulled the injector clips off and nothing changed, and i also used the logger to disable them and nothing happend. So should i try to just unplug the isc and give that a try?

 

[92awddsm]

You can unplug the isc but cold start and cold idle will suffer drastically. I personally dont run an isc and when I crank it up and try to warm it up, it is the same as an old carburated car with an inoperative choke. Be prepared to hold the gas pedal down to even get it started and to keep it idlling when cold.

Worst case senario, pm me and I will send you a good isc to try if a new or replacement isnt in the budget right now.

 

[bryce]

i can get an isc no problem, i just want to have some good feedback to see if that what is causing my problems. I just really dont wanna be ending up blowing another ecu and be back at square one. So if a bad ISC can do everything thats happening to my car then ill gladly get another one to try out and fire the thing up. Around the driver that blew up is actually pretty burnt up so it could have taken out the power for those injectors like you said. But anyway, doing the ISC will help and "should" clean up my problems correct?

 

[Loewen21]

But bryce on my ecu those things didnt burn up and it ran on two cylinders.

 

[bling5tatus]

Don't throw your ecu's away, those things are becoming rarer and rarer. Either save them for a rainy day when you're feeling froggy enough to try to reconnect the traces and replace the components on the board or give them to someone that can.

 

[bryce]

But bryce on my ecu those things didnt burn up and it ran on two cylinders.

around the chip was very burnt on yours too man, not the caps. yours looked exactly as mine did.

will this make sense for it to run on two cylinders because of it burning something else out on the board around the isc driver. Would a better pic help? If yes, what should i take the picutre of?