Steve951

I have a problem with the DME computer out of a 86 944.I have been trying to get it to idle well and had checked pretty much everything, when I noticed the ISV wasn't vibrating at all.To make a long story shorter, i plugged in a 87 turbo ecu and the valve started vibrating the way it is supposed to.

Does anyone know anything about this area in the dme or should I just get a new one?

rberry951

Try replacing just the DME eprom chips (if socketed) and if that fixes the problem it is the chip aging and loosing its programming. Very rare, but it happens. If it does not fix the problem there is very little else in the DME that is serviceable.

Regards,
Russell

Steve951

Could I just swap the turbo(ecu) chip into the NA 944 ecu to see if the idle valve comes to life?The 86 NA ecu is socketed.
Is there more than one chip to switch?
Thanks for your help.

rberry951

OH!! Wait! STOP!

I misread your original post, you cannot swap a NA/Turbo ECU! Completely different animals. I do apologize, do not attempt it or you may damage your vehicle!

Regards,
Russell

Steve951

I know I can't use the turbo ecu to drive with,I just plugged it in to see if the idle valve would run, which it did.

So do you think it would damage anything if I just swapped in the turbo dme chip, just to see if the idle valve runs?I wouldn't start the car, just turn on the ignition.

If the ISV comes to life then I can find a good NA dme chip to put in.

rberry951

Well they are the same pin wise, it certainly won't hurt the chip at all, it's just being read and they are both read the same way, applying the same voltage to the same pins, etc. So no, that won't hurt a thing. If it turns out to be the chip let me know and I'll see if I can find you another one.

Regards,
Russell

Steve951

I'll check it out tomorrow and tell you how it went.I wouldn't have thought of just the chip being bad.Hopefully it is and I can just change it.

Steve951

I switched the turbo dme chip into the NA ecu but it didn't make the ISV valve work

Steve951

Just wanted to post a follow up on what the problem ended up being.

There are 2 transistors in the dme that control the opening and closing of the ISV valve.Over time, if the isv gets dirty or dies, the transistors can burn up trying to operate the isv.

One of mine was cracked from overheating.In this first pic I have already desoldered the bad one.

You can get new transistors at radioshack for 3 bucks. T0220 TIP31.
Here is picture of the finished product.I have never soldered on a circuit board before so if I can do it anyone can.I used a 25 watt solder iron, worked great.


I also added some solder to the coil driver joints, they were all cracked.This area can cause the cutting out and no start problems.

One last thing,I got most of the info on this off a BMW board and would like to Thank them for their efforts.Here is a link to the discussion.
http://www.s14.net/forums/showthread.php?postid=77559

Regards,
Steve

The unL33T

Bringing this old thread back from ancient times, lol.


Anyone know the specs on that big brown capacitor-looking thing? 100 mF at 40V?


Mine's rusty so I figure I should replace it while I'm in there replacing other things. Guess the board got wet at some point over the years.