ECU's being fried

[Dweet]

I have a 91 TSi FWD. And every ECU I put in it is being fried. Ive been doing a little troubleshooting and I think it has something to do with pin 63 or 66. What happens is when I plug in the middle harness of the ECU (regarless if either of the two other ones are plugged in) the MPI relay goes nuts. It starts clicking on and off very rapidly. If I leave the ECU plugged in too long IC108 gets fried. Its not the relay because I've had the same results with two other relays.

Wiring Diagram for the 90-94 Turbo ECU

 

[danl]

Man, the ecu simply provides a ground for the EFI side of that coil to turn it on. The only way I could see pins 63 and 67 being damaged is if the coil was shorted causing an abnormally high current draw when the ecu grounds the other side of the coil. Pull your old MPI relay and test to see if this coil is shorted. Also try a known good MPI relay.

 

[steve]

I have a 91 TSi FWD. And every ECU I put in it is being fried. Ive been doing a little troubleshooting and I think it has something to do with pin 63 or 66. What happens is when I plug in the middle harness of the ECU (regarless if either of the two other ones are plugged in) the MPI relay goes nuts. It starts clicking on and off very rapidly. If I leave the ECU plugged in too long IC108 gets fried.

IC108 controls the EGR solenoid (pin 53) and the purge solenoid (pin 62). It sounds like one or the other is shorted to 12v.

Steve

 

[liquordrunk]

steve you said it before i could but there has to be a short somewherei suspect the egr which should be removed any way so that would take out some of the confusion.
Eliminate the EGR according to
www.taboospeedshop.com

and then if it still does it then its can only be one other thing

 

[steve]

Simplest solution is to pop both pins out of the connector and insulate them.

Depending on how much damage to the circuit traces has happened, the driver ICs can be replaced, not that you really need IC108 after disconnecting those solenoids.

The EGR solenoid only exists on CA emissions cars. The purge solenoid is for the charcoal canister under the battery. Normally both solenoids when present have coil resistance that limits the current draw when the ECU pulls the coil low with the driver. On Fed cars you shouldn't ever have battery voltage present on pin 53.

Steve

 

[liquordrunk]

Well steve your are smarter than "I". that makes more sense then what i was asking him ot do. but then again if insulating the pins might not stop if from frying it, if it does hten good, but its a good possiblity that it would be the selonoid it self and that would have ot be replaced or taken out.. and lnow where did you get the schematic to knwo that Ic chip went to those 2 parts?

 

[steve]

Not smarter, I've just been doing this sort of thing longer. I hate to think how many hours I've spent tracing what goes where and how things work. There are no schematics available to us normal humans so you wind up making your own.

I think you missed what I was trying to say, by pulling the two wires from the ECU connector they can't fry anything. You insulate then to keep them from contacting any other pins while they're loose.

There might be something else going on but that's my best educated guess as to what's happening. Dweet will have to tell us what he finds.

Steve

 

[Dweet]

so basically just cut wires 62 and 53 off of the ECU harness and insulate them and my problem is solved? sorry for taking so long to respond, i was kind of on vacation in florida the past week.

also i noticed on ECU the two circuit boards that look like they are sticking up. One of them has charred marks on it. The problem is my car craps out also at WOT. It starts bucking. I was wondering if that was also related to that other part being smoked since IC108 only controls the EGR info.

 

[BUCK]

PS Fluid leaks from hard O-Rings have killed Voltage Reg in Alternator - first hand experience!

 

[steve]

so basically just cut wires 62 and 53 off of the ECU harness and insulate them and my problem is solved? sorry for taking so long to respond, i was kind of on vacation in florida the past week.

also i noticed on ECU the two circuit boards that look like they are sticking up. One of them has charred marks on it. The problem is my car craps out also at WOT. It starts bucking. I was wondering if that was also related to that other part being smoked since IC108 only controls the EGR info.

The pins pop out easily so don't cut them off. http://www.dsmtuners.com/forums/showthread.php?t=170393

I'd have to see your ECU but it sounds like you may have other issues than just a burnt driver.

Steve

 

[Dweet]

I'll take a pic of it tomorrow. And let you see the carnage for itself

 

[Dweet]

here are a few pics if you need better ones or larger ones let me know, i just resized these

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on that bottom pic the front set of pins are fried to that circuitboard. the back set isnt

 

[steve]

I've never seen the front pins fry on that ceramic hybrid module. I seen C106 short and blow out the side covering everything with soot. When they do it usaully takes out the regulator and the board doesn't work. Perhaps one of the other parts I can't see is burned up.


Steve

 

[Dweet]

From what I can tell thats everything thats burnt up on the board. When I put in the new ECU ic108 fried right away. Nothing else is fried on it. If thats any indicator on whats going on. Like I said also my car stutters at high boost or WOT and idles at 2k RPM sometimes, other times it bounces between 1k and 1500 RPM

 

[huafist]

IC107 is fried in the picture you showed us?

 

[Dweet]

actually yes, the two were like melted together till i pushed them apart after i opened it up

 

[BUCK]

PS Fluid leaks from hard O-Rings have killed Voltage Reg in Alternator - first hand experience!

So I take it you've checked your Alt output Voltage?

 

[Dweet]

the problem occurs when the car is off and the alt is not functioning, so i doubt its the alt

 

[steve]

If IC107 fried on it's own then ou have an shorted ISC but it's possible if IC107 and IC108 where touching that IC108 burned it.

If C106 popped causing the marks on IC111 you should be able to see the marks on C106. There is nothing on the back of IC111 to burn so it has to be from one of the parts near it.

Do you still have the other two ECUs you fried?

Steve

 

[Dweet]

I have one other ECU that I fried. But now that you mention the ISC, I did replace it because the old one was bad with another used one and that might have been when the ECU problem started. I'll unplug it and try to put the semi-fried one back in and see what happens. But I dont see how that would affect the car before the ignition is turned on
could it also have the adverse effect where when IC108 shorted adnd touched 107 it caused the ISC to go bad?

 

[Dweet]

ok welllllllllllll here we go.. i removed pins 52 and 63. Now when i plug in the middle harness the problem has stopped. Before that was the only harness that needed to be plugged in for the relay to go bonkers. Now the middle harness in addition to the harness with pins 101 - 110 on it needs to be plugged in for the same result. Where do i go from here?

I dont know if this is related or not but when I put my radio back in after doing all of this the clock isnt on until i turn the ignition on. After I do that the clock never turns off. Also I noticed that when I left for florida my battery was fine, after about a week I came back and my battery was completely drained. I was wondering if there is a short somewhere that would be causing all of these problems, or if they are individual

 

[Dweet]

When I went out to my car this morning and opened the door I heard the relay noise, when I engaged the ignition it stopped for a second and then started again, but it stops completely after I start the car. It didnt make the noise since I removed 52 and 63 but now it does again unless I start the car or unplug the harness with pins 101 - 110

 

[Dweet]

I'm really thinking it has to do with wires 66 and/ or 63. I was wondering where these run and where they are terminated at

 

[steve]

I'm confused. I think you have a couple of problems.
I told you that IC108 is connected to pins 53 and 62. Disconnecting them should stop you from burning up IC108 on a good ECU. You should look at those circuits and figure out what's shorted to battery voltage.

As you can see in the Autozone diagram pins 66 and 63 are for turning on the MPI relay (63) and for monitoring (66). Without these pins your ECU can't turn the MPI power on.

If your MPI relay chatters with the ignition off but with the ECU plugged but not when the ECU is unplugged then that ECU is bad, it shouldn't be pulling 63 low until you turn the ignition switch on.

Are you trying to do this with the ECU's you have fried?

Steve

 

[Dweet]

yes because the only unfried ECU i have is a 90 with a TMO stage 3 chip and I really dont want to fry that. Thats the ECU that is going in once I get this mess sorted out. However what I dont get is with the already fried ECU that I've been running with it doesnt start chattering till about 5-10 seconds after I turn the ignition off but once the ignition is on the chattering stops the reason I think its pin 63 or 66 is because thats the wire that engages the relay and since it chatters thats why I think its that wire. However I dont understand what the ignition switch has to do with it and why it does it with the ignition off.